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<div class="section" id="the-bank-tutorial-part-2-more-examples-of-simpy-simulation">
<h1>The Bank Tutorial part 2: More examples of SimPy Simulation<a class="headerlink" href="#the-bank-tutorial-part-2-more-examples-of-simpy-simulation" title="Permalink to this headline">¶</a></h1>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Author:</th><td class="field-body">G A Vignaux</td>
</tr>
<tr class="field-even field"><th class="field-name">Date:</th><td class="field-body">2011 December</td>
</tr>
<tr class="field-odd field"><th class="field-name">SimPy release:</th><td class="field-body">2.3.1</td>
</tr>
<tr class="field-even field"><th class="field-name">Python-Version:</th><td class="field-body">2.6 and later</td>
</tr>
</tbody>
</table>
<div class="section" id="introduction">
<h2>Introduction<a class="headerlink" href="#introduction" title="Permalink to this headline">¶</a></h2>
<p>The first Bank tutorial, The Bank, developed and explained a
series of simulation models of a simple bank using <a class="reference external" href="http://simpy.sourceforge.net/">SimPy</a>. In various
models, customers arrived randomly, queued up to be served at one or
several counters, modelled using the Resource class, and, in one case,
could choose the shortest among several queues. It demonstrated the
use of the Monitor class to record delays and showed how a <tt class="docutils literal"><span class="pre">model()</span></tt>
mainline for the simulation was convenient to execute replications of
simulation runs.</p>
<p>In this extension to The Bank, I provide more examples of SimPy
facilities for which there was no room and for some that were
developed since it was written. These facilities are generally more
complicated than those introduced before. They include queueing with priority,
possibly with preemption, reneging, plotting, interrupting, waiting
until a condition occurs (<tt class="docutils literal"><span class="pre">waituntil</span></tt>) and waiting for events to
occur.</p>
<p>The programs are available without line numbers and ready to go, in
directory <tt class="docutils literal"><span class="pre">bankprograms</span></tt>. Some have trace statements for
demonstration purposes, others produce graphical output to the
screen. Let me encourage you to run them and modify them for yourself</p>
<p>SimPy itself can be obtained from: <a class="reference external" href="http://simpy.sourceforge.net/">http://simpy.sourceforge.net/</a>. It
is compatible with Python version 2.6 onwards. The examples in this
documentation run with SimPy version 1.5 and later.</p>
<p>This tutorial should be read with the SimPy Manual or Cheatsheet at
your side for reference.</p>
</div>
<div class="section" id="priority-customers">
<h2>Priority Customers<a class="headerlink" href="#priority-customers" title="Permalink to this headline">¶</a></h2>
<p>In many situations there is a system of priority service. Those
customers with high priority are served first, those with low priority
must wait. In some cases, preemptive priority will even allow a
high-priority customer to interrupt the service of one with a lower
priority.</p>
<p>SimPy implements priority requests with an extra numerical priority
argument in the <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">request</span></tt> command, higher values meaning
higher priority. For this to operate, the requested Resource must have
been defined with <tt class="docutils literal"><span class="pre">qType=PriorityQ</span></tt>.</p>
<div class="section" id="priority-customers-without-preemption">
<h3>Priority Customers without preemption<a class="headerlink" href="#priority-customers-without-preemption" title="Permalink to this headline">¶</a></h3>
<p id="index-0">In the first example, we modify the program with random arrivals, one
counter, and a fixed service time (like <tt class="docutils literal"><span class="pre">bank07.py</span></tt> in The Bank
tutorial) to process a high priority customer. Warning: the <tt class="docutils literal"><span class="pre">seed()</span></tt>
value has been changed to <tt class="docutils literal"><span class="pre">98989</span></tt> to make the story more exciting.</p>
<p>The modifications are to the definition of the <tt class="docutils literal"><span class="pre">counter</span></tt> where we
change the <tt class="docutils literal"><span class="pre">qType</span></tt> and to the <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">request</span></tt> command in the
<tt class="docutils literal"><span class="pre">visit</span></tt> PEM of the customer. We also need to provide each customer
with a priority. Since the default is <tt class="docutils literal"><span class="pre">priority=0</span></tt> this is easy for
most of them.</p>
<p>To observe the priority in action, while all other customers have the
default priority of 0, in lines 46 to 48 we create and
activate one special customer, <tt class="docutils literal"><span class="pre">Guido</span></tt>, with priority 100 who
arrives at time <tt class="docutils literal"><span class="pre">23.0</span></tt> (line 48). This is to ensure that he arrives
after <tt class="docutils literal"><span class="pre">Customer03</span></tt>.</p>
<p>The <tt class="docutils literal"><span class="pre">visit</span></tt> customer method has a new parameter, <tt class="docutils literal"><span class="pre">P=0</span></tt> (line
21) which allows us to set the customer priority.</p>
<p>In lines 38 to 38 <tt class="docutils literal"><span class="pre">counter</span></tt> is defined with <tt class="docutils literal"><span class="pre">qType=PriorityQ</span></tt> so
that we can request it with priority (line 26) using the
statement <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">request,self,counter,P</span></tt></p>
<p>In line 24 we print out the number of customers waiting when each
customer arrives.</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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51</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">""" bank20: One counter with a priority customer """</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="n">expovariate</span><span class="p">,</span> <span class="n">seed</span>
<span class="c">## Model components ------------------------</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly """</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">interval</span><span class="p">,</span> <span class="n">resource</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">,</span>
<span class="n">res</span><span class="o">=</span><span class="n">resource</span><span class="p">,</span> <span class="n">P</span><span class="o">=</span><span class="mi">0</span><span class="p">))</span>
<span class="n">t</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">interval</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">t</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">res</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">P</span><span class="o">=</span><span class="mi">0</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="c"># arrival time</span>
<span class="n">Nwaiting</span> <span class="o">=</span> <span class="nb">len</span><span class="p">(</span><span class="n">res</span><span class="o">.</span><span class="n">waitQ</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Queue is </span><span class="si">%d</span><span class="s"> on arrival"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">Nwaiting</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">res</span><span class="p">,</span> <span class="n">P</span>
<span class="n">wait</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="o">-</span> <span class="n">arrive</span> <span class="c"># waiting time</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Waited </span><span class="si">%6.3f</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">wait</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">res</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Completed"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">400.0</span> <span class="c"># minutes</span>
<span class="n">k</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Counter"</span><span class="p">,</span> <span class="n">unitName</span><span class="o">=</span><span class="s">"Karen"</span><span class="p">,</span>
<span class="n">qType</span><span class="o">=</span><span class="n">PriorityQ</span><span class="p">)</span>
<span class="c">## Model/Experiment ------------------------------</span>
<span class="n">seed</span><span class="p">(</span><span class="mi">98989</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">Source</span><span class="p">(</span><span class="s">'Source'</span><span class="p">)</span>
<span class="n">activate</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">s</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span> <span class="n">interval</span><span class="o">=</span><span class="mf">10.0</span><span class="p">,</span>
<span class="n">resource</span><span class="o">=</span><span class="n">k</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">guido</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Guido "</span><span class="p">)</span>
<span class="n">activate</span><span class="p">(</span><span class="n">guido</span><span class="p">,</span> <span class="n">guido</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">,</span> <span class="n">res</span><span class="o">=</span><span class="n">k</span><span class="p">,</span>
<span class="n">P</span><span class="o">=</span><span class="mi">100</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">23.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
</pre></div>
</td></tr></table></div>
<p>The resulting output is as follows. The number of customers in the
queue just as each arrives is displayed in the trace. That count does
not include any customer in service.</p>
<div class="highlight-python"><pre> 0.000 Customer00: Queue is 0 on arrival
0.000 Customer00: Waited 0.000
12.000 Customer00: Completed
16.359 Customer01: Queue is 0 on arrival
16.359 Customer01: Waited 0.000
23.000 Guido : Queue is 0 on arrival
28.359 Customer01: Completed
28.359 Guido : Waited 5.359
29.991 Customer02: Queue is 0 on arrival
35.776 Customer03: Queue is 1 on arrival
36.650 Customer04: Queue is 2 on arrival
40.359 Guido : Completed
40.359 Customer02: Waited 10.368
52.359 Customer02: Completed
52.359 Customer03: Waited 16.583
64.359 Customer03: Completed
64.359 Customer04: Waited 27.709
76.359 Customer04: Completed
</pre>
</div>
<p id="index-1">Reading carefully one can see that when <tt class="docutils literal"><span class="pre">Guido</span></tt> arrives
<tt class="docutils literal"><span class="pre">Customer00</span></tt> has been served and left at <tt class="docutils literal"><span class="pre">12.000</span></tt>), <tt class="docutils literal"><span class="pre">Customer01</span></tt>
is in service and two (customers 02 and 03) are queueing. <tt class="docutils literal"><span class="pre">Guido</span></tt>
has priority over those waiting and is served before them at
<tt class="docutils literal"><span class="pre">33.162</span></tt>. When <tt class="docutils literal"><span class="pre">Guido</span></tt> leaves at <tt class="docutils literal"><span class="pre">45.162</span></tt>, <tt class="docutils literal"><span class="pre">Customer02</span></tt> starts
service.</p>
</div>
<div class="section" id="priority-customers-with-preemption">
<h3>Priority Customers with preemption<a class="headerlink" href="#priority-customers-with-preemption" title="Permalink to this headline">¶</a></h3>
<p id="index-2">Now we allow <tt class="docutils literal"><span class="pre">Guido</span></tt> to have preemptive priority. He will displace
any customer in service when he arrives. That customer will resume
when <tt class="docutils literal"><span class="pre">Guido</span></tt> finishes (unless higher priority customers
intervene). It requires only a change to one line of the program,
adding the argument, <tt class="docutils literal"><span class="pre">preemptable=True</span></tt> to the <tt class="docutils literal"><span class="pre">Resource</span></tt>
statement in line 38.</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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51</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">""" bank23: One counter with a priority customer with preemption """</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="n">expovariate</span><span class="p">,</span> <span class="n">seed</span>
<span class="c">## Model components ------------------------</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly """</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">interval</span><span class="p">,</span> <span class="n">resource</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">,</span>
<span class="n">res</span><span class="o">=</span><span class="n">resource</span><span class="p">,</span> <span class="n">P</span><span class="o">=</span><span class="mi">0</span><span class="p">))</span>
<span class="n">t</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">interval</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">t</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">res</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span> <span class="n">P</span><span class="o">=</span><span class="mi">0</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="c"># arrival time</span>
<span class="n">Nwaiting</span> <span class="o">=</span> <span class="nb">len</span><span class="p">(</span><span class="n">res</span><span class="o">.</span><span class="n">waitQ</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Queue is </span><span class="si">%d</span><span class="s"> on arrival"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">Nwaiting</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">res</span><span class="p">,</span> <span class="n">P</span>
<span class="n">wait</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="o">-</span> <span class="n">arrive</span> <span class="c"># waiting time</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Waited </span><span class="si">%6.3f</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">wait</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">res</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Completed"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">400.0</span> <span class="c"># minutes</span>
<span class="n">k</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Counter"</span><span class="p">,</span> <span class="n">unitName</span><span class="o">=</span><span class="s">"Karen"</span><span class="p">,</span>
<span class="n">qType</span><span class="o">=</span><span class="n">PriorityQ</span><span class="p">,</span> <span class="n">preemptable</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="c">## Model/Experiment ------------------------------</span>
<span class="n">seed</span><span class="p">(</span><span class="mi">98989</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">Source</span><span class="p">(</span><span class="s">'Source'</span><span class="p">)</span>
<span class="n">activate</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">s</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span> <span class="n">interval</span><span class="o">=</span><span class="mf">10.0</span><span class="p">,</span>
<span class="n">resource</span><span class="o">=</span><span class="n">k</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">guido</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Guido "</span><span class="p">)</span>
<span class="n">activate</span><span class="p">(</span><span class="n">guido</span><span class="p">,</span> <span class="n">guido</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">,</span> <span class="n">res</span><span class="o">=</span><span class="n">k</span><span class="p">,</span>
<span class="n">P</span><span class="o">=</span><span class="mi">100</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">23.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
</pre></div>
</td></tr></table></div>
<p>Though <tt class="docutils literal"><span class="pre">Guido</span></tt> arrives at the same time, <tt class="docutils literal"><span class="pre">23.000</span></tt>, he no longer
has to wait and immediately goes into service, displacing the
incumbent, <tt class="docutils literal"><span class="pre">Customer01</span></tt>. That customer had already completed
<tt class="docutils literal"><span class="pre">23.000-12.000</span> <span class="pre">=</span> <span class="pre">11.000</span></tt> minutes of his service. When <tt class="docutils literal"><span class="pre">Guido</span></tt>
finishes at <tt class="docutils literal"><span class="pre">35.000</span></tt>, <tt class="docutils literal"><span class="pre">Customer01</span></tt> resumes service and takes
<tt class="docutils literal"><span class="pre">36.000-35.000</span> <span class="pre">=</span> <span class="pre">1.000</span></tt> minutes to finish. His total service time
is the same as before (<tt class="docutils literal"><span class="pre">12.000</span></tt> minutes).</p>
<div class="highlight-python"><pre> 0.000 Customer00: Queue is 0 on arrival
0.000 Customer00: Waited 0.000
12.000 Customer00: Completed
16.359 Customer01: Queue is 0 on arrival
16.359 Customer01: Waited 0.000
23.000 Guido : Queue is 0 on arrival
23.000 Guido : Waited 0.000
29.991 Customer02: Queue is 1 on arrival
35.000 Guido : Completed
35.776 Customer03: Queue is 1 on arrival
36.650 Customer04: Queue is 2 on arrival
40.359 Customer01: Completed
40.359 Customer02: Waited 10.368
52.359 Customer02: Completed
52.359 Customer03: Waited 16.583
64.359 Customer03: Completed
64.359 Customer04: Waited 27.709
76.359 Customer04: Completed
</pre>
</div>
</div>
</div>
<div class="section" id="balking-and-reneging-customers">
<h2>Balking and Reneging Customers<a class="headerlink" href="#balking-and-reneging-customers" title="Permalink to this headline">¶</a></h2>
<p id="index-3">Balking occurs when a customer refuses to join a queue if it is too
long. Reneging (or, better, abandonment) occurs if an impatient
customer gives up while still waiting and before being served.</p>
<div class="section" id="balking-customers">
<h3>Balking Customers<a class="headerlink" href="#balking-customers" title="Permalink to this headline">¶</a></h3>
<p id="index-4">Another term for a system with balking customers is one where “blocked
customers” are “cleared”, termed by engineers a BCC system. This is
very convenient analytically in queueing theory and formulae developed
using this assumption are used extensively for planning communication
systems. The easiest case is when no queueing is allowed.</p>
<p>As an example let us investigate a BCC system with a single server but
the waiting space is limited. We will estimate the rate of balking
when the maximum number in the queue is set to 1. On arrival into the
system the customer must first check to see if there is room. We will
need the number of customers in the system or waiting. We could keep a
count, incrementing when a customer joins the queue or, since we have
a Resource, use the length of the Resource’s <tt class="docutils literal"><span class="pre">waitQ</span></tt>. Choosing the
latter we test (on line 25). If there is not enough room, we
balk, incrementing a Class variable <tt class="docutils literal"><span class="pre">Customer.numBalking</span></tt> at line
34 to get the total number balking during the run.</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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66</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">""" bank24. BCC system with several counters """</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="n">expovariate</span><span class="p">,</span> <span class="n">seed</span>
<span class="c">## Model components ------------------------</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly """</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">meanTBA</span><span class="p">,</span> <span class="n">resource</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">b</span><span class="o">=</span><span class="n">resource</span><span class="p">))</span>
<span class="n">t</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">meanTBA</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">t</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="n">numBalking</span> <span class="o">=</span> <span class="mi">0</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">b</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Here I am "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">b</span><span class="o">.</span><span class="n">waitQ</span><span class="p">)</span> <span class="o"><</span> <span class="n">maxInQueue</span><span class="p">:</span> <span class="c"># the test</span>
<span class="k">yield</span> <span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">b</span>
<span class="n">wait</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="o">-</span> <span class="n">arrive</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Wait </span><span class="si">%6.3f</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">wait</span><span class="p">))</span>
<span class="n">tib</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">timeInBank</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">tib</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">b</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Finished "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">Customer</span><span class="o">.</span><span class="n">numBalking</span> <span class="o">+=</span> <span class="mi">1</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: BALKING "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="c">## Experiment data -------------------------------</span>
<span class="n">timeInBank</span> <span class="o">=</span> <span class="mf">12.0</span> <span class="c"># mean, minutes</span>
<span class="n">ARRint</span> <span class="o">=</span> <span class="mf">10.0</span> <span class="c"># mean interarrival time, minutes</span>
<span class="n">numServers</span> <span class="o">=</span> <span class="mi">1</span> <span class="c"># servers</span>
<span class="n">maxInSystem</span> <span class="o">=</span> <span class="mi">2</span> <span class="c"># customers</span>
<span class="n">maxInQueue</span> <span class="o">=</span> <span class="n">maxInSystem</span> <span class="o">-</span> <span class="n">numServers</span>
<span class="n">maxNumber</span> <span class="o">=</span> <span class="mi">8</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">4000.0</span> <span class="c"># minutes</span>
<span class="n">theseed</span> <span class="o">=</span> <span class="mi">12345</span>
<span class="c">## Model/Experiment ------------------------------</span>
<span class="n">seed</span><span class="p">(</span><span class="n">theseed</span><span class="p">)</span>
<span class="n">k</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="n">capacity</span><span class="o">=</span><span class="n">numServers</span><span class="p">,</span>
<span class="n">name</span><span class="o">=</span><span class="s">"Counter"</span><span class="p">,</span> <span class="n">unitName</span><span class="o">=</span><span class="s">"Clerk"</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">Source</span><span class="p">(</span><span class="s">'Source'</span><span class="p">)</span>
<span class="n">activate</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">s</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="n">maxNumber</span><span class="p">,</span> <span class="n">meanTBA</span><span class="o">=</span><span class="n">ARRint</span><span class="p">,</span>
<span class="n">resource</span><span class="o">=</span><span class="n">k</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
<span class="c">## Results -----------------------------------------</span>
<span class="n">nb</span> <span class="o">=</span> <span class="nb">float</span><span class="p">(</span><span class="n">Customer</span><span class="o">.</span><span class="n">numBalking</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">"balking rate is </span><span class="si">%8.4f</span><span class="s"> per minute"</span> <span class="o">%</span> <span class="p">(</span><span class="n">nb</span> <span class="o">/</span> <span class="n">now</span><span class="p">()))</span>
</pre></div>
</td></tr></table></div>
<p>The resulting output for a run of this program showing balking
occurring is given below:</p>
<div class="highlight-python"><pre> 0.0000 Customer00: Here I am
0.0000 Customer00: Wait 0.000
0.1227 Customer00: Finished
5.3892 Customer01: Here I am
5.3892 Customer01: Wait 0.000
9.6460 Customer01: Finished
22.8307 Customer02: Here I am
22.8307 Customer02: Wait 0.000
25.4137 Customer02: Finished
27.4258 Customer03: Here I am
27.4258 Customer03: Wait 0.000
29.5422 Customer03: Finished
35.7731 Customer04: Here I am
35.7731 Customer04: Wait 0.000
37.1001 Customer05: Here I am
42.5805 Customer04: Finished
42.5805 Customer05: Wait 5.480
44.8795 Customer05: Finished
45.3572 Customer06: Here I am
45.3572 Customer06: Wait 0.000
50.6175 Customer06: Finished
53.4141 Customer07: Here I am
53.4141 Customer07: Wait 0.000
54.5629 Customer07: Finished
balking rate is 0.0000 per minute
</pre>
</div>
<p>When <tt class="docutils literal"><span class="pre">Customer02</span></tt> arrives, numbers 00 is already in service and 01
is waiting. There is no room so 02 balks. By the vagaries of
exponential random numbers, 00 takes a very long time to serve (55.0607
minutes) so the first one to find room is number 07 at 73.0765.</p>
</div>
<div class="section" id="reneging-or-abandoning-customers">
<h3>Reneging (or abandoning) Customers<a class="headerlink" href="#reneging-or-abandoning-customers" title="Permalink to this headline">¶</a></h3>
<p>Often in practice an impatient customer will leave the queue before
being served. SimPy can model this <em>reneging</em> behaviour using a
<em>compound yield statement</em>. In such a statement there are two
yield clauses. An example is:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">yield</span> <span class="p">(</span><span class="n">request</span><span class="p">,</span><span class="bp">self</span><span class="p">,</span><span class="n">counter</span><span class="p">),(</span><span class="n">hold</span><span class="p">,</span><span class="bp">self</span><span class="p">,</span><span class="n">maxWaitTime</span><span class="p">)</span>
</pre></div>
</div>
<p>The first tuple of this statement is the usual <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">request</span></tt>,
asking for a unit of <tt class="docutils literal"><span class="pre">counter</span></tt> Resource. The process will either get
the unit immediately or be queued by the Resource. The second tuple is
a reneging clause which has the same syntax as a <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">hold</span></tt>. The
requesting process will renege if the wait exceeds <tt class="docutils literal"><span class="pre">maxWaitTime</span></tt>.</p>
<p>There is a complication, though. The requesting PEM must discover what
actually happened. Did the process get the resource or did it
renege? This involves a <em>mandatory</em> test of <tt class="docutils literal"><span class="pre">self.acquired(</span></tt><em>resource</em><tt class="docutils literal"><span class="pre">)</span></tt>. In our example, this test is in line 26.</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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56</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">""" bank21: One counter with impatient customers """</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="n">expovariate</span><span class="p">,</span> <span class="n">seed</span>
<span class="c">## Model components ------------------------</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly """</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">interval</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">15.0</span><span class="p">))</span>
<span class="n">t</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">interval</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">t</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="o">=</span><span class="mi">0</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="c"># arrival time</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Here I am "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">yield</span> <span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span><span class="p">),</span> <span class="p">(</span><span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">maxWaitTime</span><span class="p">)</span>
<span class="n">wait</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="o">-</span> <span class="n">arrive</span> <span class="c"># waiting time</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">acquired</span><span class="p">(</span><span class="n">counter</span><span class="p">):</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Waited </span><span class="si">%6.3f</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">wait</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Completed"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">else</span><span class="p">:</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.3f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Waited </span><span class="si">%6.3f</span><span class="s">. I am off"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">wait</span><span class="p">))</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">400.0</span> <span class="c"># minutes</span>
<span class="n">maxWaitTime</span> <span class="o">=</span> <span class="mf">12.0</span> <span class="c"># minutes. maximum time to wait</span>
<span class="c">## Model ----------------------------------</span>
<span class="k">def</span> <span class="nf">model</span><span class="p">():</span>
<span class="k">global</span> <span class="n">counter</span>
<span class="n">seed</span><span class="p">(</span><span class="mi">98989</span><span class="p">)</span>
<span class="n">counter</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Karen"</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">source</span> <span class="o">=</span> <span class="n">Source</span><span class="p">(</span><span class="s">'Source'</span><span class="p">)</span>
<span class="n">activate</span><span class="p">(</span><span class="n">source</span><span class="p">,</span>
<span class="n">source</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span> <span class="n">interval</span><span class="o">=</span><span class="mf">10.0</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
<span class="c">## Experiment ----------------------------------</span>
<span class="n">model</span><span class="p">()</span>
</pre></div>
</td></tr></table></div>
<div class="highlight-python"><pre> 0.000 Customer00: Here I am
0.000 Customer00: Waited 0.000
15.000 Customer00: Completed
16.359 Customer01: Here I am
16.359 Customer01: Waited 0.000
29.991 Customer02: Here I am
31.359 Customer01: Completed
31.359 Customer02: Waited 1.368
35.776 Customer03: Here I am
36.650 Customer04: Here I am
46.359 Customer02: Completed
46.359 Customer03: Waited 10.583
48.650 Customer04: Waited 12.000. I am off
61.359 Customer03: Completed
</pre>
</div>
<p><tt class="docutils literal"><span class="pre">Customer01</span></tt> arrives after 00 but has only 12 minutes
patience. After that time in the queue (at time 14.166) he abandons
the queue to leave 02 to take his place. 03 also abandons. 04 finds an
empty system and takes the server without having to wait.</p>
</div>
</div>
<div class="section" id="processes">
<h2>Processes<a class="headerlink" href="#processes" title="Permalink to this headline">¶</a></h2>
<p>In some simulations it is valuable for one SimPy Process to interrupt
another. This can only be done when the <em>victim</em> is “active”; that is
when it has an event scheduled for it. It must be executing a <tt class="docutils literal"><span class="pre">yield</span>
<span class="pre">hold</span></tt> statement.</p>
<p>A process waiting for a resource (after a <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">request</span></tt>
statement) is passive and cannot be interrupted by another. Instead
the <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">waituntil</span></tt> and <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">waitevent</span></tt> facilities have been
introduced to allow processes to wait for conditions set by other
processes.</p>
<div class="section" id="interrupting-a-process">
<h3>Interrupting a Process.<a class="headerlink" href="#interrupting-a-process" title="Permalink to this headline">¶</a></h3>
<p><tt class="docutils literal"><span class="pre">Klaus</span></tt> goes into the bank to talk to the manager. For clarity we
ignore the counters and other customers. During his conversation his
cellphone rings. When he finishes the call he continues the
conversation.</p>
<p>In this example, <tt class="docutils literal"><span class="pre">call</span></tt> is an object of the <tt class="docutils literal"><span class="pre">Call</span></tt> Process class
whose only purpose is to make the cellphone ring after a delay,
<tt class="docutils literal"><span class="pre">timeOfCall</span></tt>, an argument to its <tt class="docutils literal"><span class="pre">ring</span></tt> PEM (line 26).</p>
<p><tt class="docutils literal"><span class="pre">klaus</span></tt>, a <tt class="docutils literal"><span class="pre">Customer</span></tt>, is interrupted by the call (line 29).
He is in the middle of a <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">hold</span></tt> (line 12). When he exits
from that command it is as if he went into a trance when talking to
the bank manager. He suddenly wakes up and must check (line 13)
to see whether has finished his conversation (if there was no call) or
has been interrupted.</p>
<p>If <tt class="docutils literal"><span class="pre">self.interrupted()</span></tt> is <tt class="docutils literal"><span class="pre">False</span></tt> he was not interrupted and
leaves the bank (line 21) normally. If it is <tt class="docutils literal"><span class="pre">True</span></tt>, he was
interrupted by the call, remembers how much conversation he has left
(line 14), resets the interrupt (line 15) and then deals
with the call. When he finishes (line 19) he can resume the
conversation, with, now we assume, a thoroughly irritated bank manager
v(line 20).</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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47</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">""" bank22: An interruption by a phone call """</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="c">## Model components ------------------------</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, looks around and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="p">,</span> <span class="n">onphone</span><span class="p">):</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Here I am"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">interrupted</span><span class="p">():</span>
<span class="n">timeleft</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">interruptLeft</span>
<span class="bp">self</span><span class="o">.</span><span class="n">interruptReset</span><span class="p">()</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Excuse me"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Hello! I'll call back"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">onphone</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Sorry, where were we?"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">timeleft</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: I must leave"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">class</span> <span class="nc">Call</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Cellphone call arrives and interrupts """</span>
<span class="k">def</span> <span class="nf">ring</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">klaus</span><span class="p">,</span> <span class="n">timeOfCall</span><span class="p">):</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">timeOfCall</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> Ringgg!"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">()))</span>
<span class="bp">self</span><span class="o">.</span><span class="n">interrupt</span><span class="p">(</span><span class="n">klaus</span><span class="p">)</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">timeInBank</span> <span class="o">=</span> <span class="mf">20.0</span>
<span class="n">timeOfCall</span> <span class="o">=</span> <span class="mf">9.0</span>
<span class="n">onphone</span> <span class="o">=</span> <span class="mf">3.0</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">100.0</span>
<span class="c">## Model/Experiment ----------------------------------</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">klaus</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Klaus"</span><span class="p">)</span>
<span class="n">activate</span><span class="p">(</span><span class="n">klaus</span><span class="p">,</span> <span class="n">klaus</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="p">,</span> <span class="n">onphone</span><span class="p">))</span>
<span class="n">call</span> <span class="o">=</span> <span class="n">Call</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"klaus"</span><span class="p">)</span>
<span class="n">activate</span><span class="p">(</span><span class="n">call</span><span class="p">,</span> <span class="n">call</span><span class="o">.</span><span class="n">ring</span><span class="p">(</span><span class="n">klaus</span><span class="p">,</span> <span class="n">timeOfCall</span><span class="p">))</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
</pre></div>
</td></tr></table></div>
<div class="highlight-python"><pre> 0.0000 Klaus: Here I am
9.0000 Ringgg!
9.0000 Klaus: Excuse me
9.0000 Klaus: Hello! I'll call back
12.0000 Klaus: Sorry, where were we?
23.0000 Klaus: I must leave
</pre>
</div>
<p>As this has no random numbers the results are reasonably clear: the
interrupting call occurs at 9.0. It takes <tt class="docutils literal"><span class="pre">klaus</span></tt> 3 minutes to
listen to the message and he resumes the conversation with the bank
manager at 12.0. His total time of conversation is 9.0 + 11.0 = 20.0
minutes as it would have been if the interrupt had not occurred.</p>
</div>
<div class="section" id="waituntil-the-bank-door-opens">
<h3><tt class="docutils literal"><span class="pre">waituntil</span></tt> the Bank door opens<a class="headerlink" href="#waituntil-the-bank-door-opens" title="Permalink to this headline">¶</a></h3>
<p>Customers arrive at random, some of them getting to the bank before
the door is opened by a doorman. They wait for the door to be opened
and then rush in and queue to be served.</p>
<p>This model uses the <tt class="docutils literal"><span class="pre">waituntil</span></tt> yield command. In the program listing
the door is initially closed (line 7) and a function to test if
it is open is defined at line 8.</p>
<p>The <tt class="docutils literal"><span class="pre">Doorman</span></tt> class is defined starting at line 11 and the single
<tt class="docutils literal"><span class="pre">doorman</span></tt> is created and activated at at lines 65 and 66. The
doorman waits for an average 10 minutes (label 16) and then
opens the door.</p>
<p>The <tt class="docutils literal"><span class="pre">Customer</span></tt> class is defined at 29 and a new customer prints out
<tt class="docutils literal"><span class="pre">Here</span> <span class="pre">I</span> <span class="pre">am</span></tt> on arrival. If the door is still closed, he adds <tt class="docutils literal"><span class="pre">but</span>
<span class="pre">the</span> <span class="pre">door</span> <span class="pre">is</span> <span class="pre">shut</span></tt> and settles down to wait (line 40), using the
<tt class="docutils literal"><span class="pre">yield</span> <span class="pre">waituntil</span></tt> command. When the door is opened by the doorman the
<tt class="docutils literal"><span class="pre">dooropen</span></tt> state is changed and the customer (and all others waiting
for the door) proceed. A customer arriving when the door is open will
not be delayed.</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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80</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">"""bank14: *waituntil* the Bank door opens"""</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="n">expovariate</span><span class="p">,</span> <span class="n">seed</span>
<span class="c">## Model components ------------------------</span>
<span class="n">door</span> <span class="o">=</span> <span class="s">'Shut'</span>
<span class="k">def</span> <span class="nf">dooropen</span><span class="p">():</span>
<span class="k">return</span> <span class="n">door</span> <span class="o">==</span> <span class="s">'Open'</span>
<span class="k">class</span> <span class="nc">Doorman</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Doorman opens the door"""</span>
<span class="k">def</span> <span class="nf">openthedoor</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">""" He will open the door when he arrives"""</span>
<span class="k">global</span> <span class="n">door</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="mf">10.0</span><span class="p">)</span>
<span class="n">door</span> <span class="o">=</span> <span class="s">'Open'</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> Doorman: Ladies and "</span>\
<span class="s">"Gentlemen! You may all enter."</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">()))</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly"""</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">rate</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">expovariate</span><span class="p">(</span><span class="n">rate</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="o">=</span><span class="mi">10</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span>
<span class="k">if</span> <span class="n">dooropen</span><span class="p">():</span>
<span class="n">msg</span> <span class="o">=</span> <span class="s">' and the door is open.'</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">msg</span> <span class="o">=</span> <span class="s">' but the door is shut.'</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Here I am</span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">msg</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">waituntil</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">dooropen</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: I can go in!"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="n">wait</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="o">-</span> <span class="n">arrive</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Waited </span><span class="si">%6.3f</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">wait</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="n">tib</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">timeInBank</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">tib</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Finished "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">2000.0</span> <span class="c"># minutes</span>
<span class="n">counter</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s">"Clerk"</span><span class="p">)</span>
<span class="c">## Model ----------------------------------</span>
<span class="k">def</span> <span class="nf">model</span><span class="p">(</span><span class="n">SEED</span><span class="o">=</span><span class="mi">393939</span><span class="p">):</span>
<span class="n">seed</span><span class="p">(</span><span class="n">SEED</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">door</span> <span class="o">=</span> <span class="s">'Shut'</span>
<span class="n">doorman</span> <span class="o">=</span> <span class="n">Doorman</span><span class="p">()</span>
<span class="n">activate</span><span class="p">(</span><span class="n">doorman</span><span class="p">,</span> <span class="n">doorman</span><span class="o">.</span><span class="n">openthedoor</span><span class="p">())</span>
<span class="n">source</span> <span class="o">=</span> <span class="n">Source</span><span class="p">()</span>
<span class="n">activate</span><span class="p">(</span><span class="n">source</span><span class="p">,</span>
<span class="n">source</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span> <span class="n">rate</span><span class="o">=</span><span class="mf">0.1</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="mf">400.0</span><span class="p">)</span>
<span class="c">## Experiment ----------------------------------</span>
<span class="n">model</span><span class="p">()</span>
</pre></div>
</td></tr></table></div>
<p>An output run for this programs shows how the first three customers
have to wait until the door is opened.</p>
<div class="highlight-python"><pre> 0.0000 Customer00: Here I am but the door is shut.
1.1489 Doorman: Ladies and Gentlemen! You may all enter.
1.1489 Customer00: I can go in!
1.1489 Customer00: Waited 1.149
6.5691 Customer00: Finished
8.3438 Customer01: Here I am and the door is open.
8.3438 Customer01: I can go in!
8.3438 Customer01: Waited 0.000
15.5704 Customer02: Here I am and the door is open.
15.5704 Customer02: I can go in!
15.5704 Customer02: Waited 0.000
21.2664 Customer03: Here I am and the door is open.
21.2664 Customer03: I can go in!
21.2664 Customer03: Waited 0.000
21.9473 Customer04: Here I am and the door is open.
21.9473 Customer04: I can go in!
21.9473 Customer04: Waited 0.000
27.6401 Customer01: Finished
56.5248 Customer02: Finished
57.3640 Customer03: Finished
77.3587 Customer04: Finished
</pre>
</div>
</div>
<div class="section" id="wait-for-the-doorman-to-give-a-signal-waitevent">
<h3>Wait for the doorman to give a signal: <tt class="docutils literal"><span class="pre">waitevent</span></tt><a class="headerlink" href="#wait-for-the-doorman-to-give-a-signal-waitevent" title="Permalink to this headline">¶</a></h3>
<p>Customers arrive at random, some of them getting to the bank before
the door is open. This is controlled by an automatic machine called
the doorman which opens the door only at intervals of 30 minutes (it
is a very secure bank). The customers wait for the door to be opened
and all those waiting enter and proceed to the counter. The door is
closed behind them.</p>
<p>This model uses the <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">waitevent</span></tt> command which requires a
<tt class="docutils literal"><span class="pre">SimEvent</span></tt> to be defined (line 7). The <tt class="docutils literal"><span class="pre">Doorman</span></tt> class is defined
at line 8 and the <tt class="docutils literal"><span class="pre">doorman</span></tt> is created and activated at at labels
61 and 62. The doorman waits for a fixed time (label
13) and then tells the customers that the door is open. This is
achieved on line 14 by signalling the <tt class="docutils literal"><span class="pre">dooropen</span></tt> event.</p>
<p>The <tt class="docutils literal"><span class="pre">Customer</span></tt> class is defined at 25 and in its PEM, when a
customer arrives, he prints out <tt class="docutils literal"><span class="pre">Here</span> <span class="pre">I</span> <span class="pre">am</span></tt>. If the door is still
closed, he adds <cite>“but the door is shut`</cite> and settles down to wait for
the door to be opened using the <tt class="docutils literal"><span class="pre">yield</span> <span class="pre">waitevent</span></tt> command (line
35). When the door is opened by the doorman (that is, he sends
the <tt class="docutils literal"><span class="pre">dooropen.signal()</span></tt> the customer and any others waiting may
proceed.</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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76</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">""" bank13: Wait for the doorman to give a signal: *waitevent*"""</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="o">*</span>
<span class="c">## Model components ------------------------</span>
<span class="n">dooropen</span> <span class="o">=</span> <span class="n">SimEvent</span><span class="p">(</span><span class="s">"Door Open"</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Doorman</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Doorman opens the door"""</span>
<span class="k">def</span> <span class="nf">openthedoor</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">""" He will opens the door at fixed intervals"""</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">5</span><span class="p">):</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="mf">30.0</span>
<span class="n">dooropen</span><span class="o">.</span><span class="n">signal</span><span class="p">()</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> You may enter"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">()))</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly"""</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">rate</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">expovariate</span><span class="p">(</span><span class="n">rate</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="o">=</span><span class="mi">10</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span>
<span class="k">if</span> <span class="n">dooropen</span><span class="o">.</span><span class="n">occurred</span><span class="p">:</span>
<span class="n">msg</span> <span class="o">=</span> <span class="s">'.'</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">msg</span> <span class="o">=</span> <span class="s">' but the door is shut.'</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Here I am</span><span class="si">%s</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">msg</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">waitevent</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">dooropen</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: The door is open!"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="n">wait</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="o">-</span> <span class="n">arrive</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Waited </span><span class="si">%6.3f</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">wait</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="n">tib</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">timeInBank</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">tib</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%7.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Finished "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">400.0</span> <span class="c"># minutes</span>
<span class="n">counter</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s">"Clerk"</span><span class="p">)</span>
<span class="c">## Model ----------------------------------</span>
<span class="k">def</span> <span class="nf">model</span><span class="p">(</span><span class="n">SEED</span><span class="o">=</span><span class="mi">393939</span><span class="p">):</span>
<span class="n">seed</span><span class="p">(</span><span class="n">SEED</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">doorman</span> <span class="o">=</span> <span class="n">Doorman</span><span class="p">()</span>
<span class="n">activate</span><span class="p">(</span><span class="n">doorman</span><span class="p">,</span> <span class="n">doorman</span><span class="o">.</span><span class="n">openthedoor</span><span class="p">())</span>
<span class="n">source</span> <span class="o">=</span> <span class="n">Source</span><span class="p">()</span>
<span class="n">activate</span><span class="p">(</span><span class="n">source</span><span class="p">,</span>
<span class="n">source</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span> <span class="n">rate</span><span class="o">=</span><span class="mf">0.1</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
<span class="c">## Experiment ----------------------------------</span>
<span class="n">model</span><span class="p">()</span>
</pre></div>
</td></tr></table></div>
<p>An output run for this programs shows how the first three customers
have to wait until the door is opened.</p>
<div class="highlight-python"><pre> 0.0000 Customer00: Here I am but the door is shut.
1.1489 Customer01: Here I am but the door is shut.
9.4928 Customer02: Here I am but the door is shut.
14.0096 Customer03: Here I am but the door is shut.
21.2361 Customer04: Here I am but the door is shut.
30.0000 You may enter
30.0000 Customer04: The door is open!
30.0000 Customer04: Waited 8.764
30.0000 Customer03: The door is open!
30.0000 Customer03: Waited 15.990
30.0000 Customer02: The door is open!
30.0000 Customer02: Waited 20.507
30.0000 Customer01: The door is open!
30.0000 Customer01: Waited 28.851
30.0000 Customer00: The door is open!
30.0000 Customer00: Waited 30.000
36.8352 Customer04: Finished
37.6524 Customer03: Finished
52.4654 Customer02: Finished
60.0000 You may enter
81.3502 Customer01: Finished
82.1893 Customer00: Finished
90.0000 You may enter
120.0000 You may enter
150.0000 You may enter
</pre>
</div>
</div>
</div>
<div class="section" id="monitors">
<h2>Monitors<a class="headerlink" href="#monitors" title="Permalink to this headline">¶</a></h2>
<p>Monitors (and Tallys) are used to track and record values in a
simulation. They store a list of [time,value] pairs, one pair being
added whenever the <tt class="docutils literal"><span class="pre">observe</span></tt> method is called. A particularly
useful characteristic is that they continue to exist after the
simulation has been completed. Thus further analysis of the results
can be carried out.</p>
<p>Monitors have a set of simple statistical methods such as <tt class="docutils literal"><span class="pre">mean</span></tt> and
<tt class="docutils literal"><span class="pre">var</span></tt> to calculate the average and variance of the observed values
– useful in estimating the mean delay, for example.</p>
<p>They also have the <tt class="docutils literal"><span class="pre">timeAverage</span></tt> method that calculates the
time-weighted average of the recorded values. It determines the total
area under the time~value graph and divides by the total time. This is
useful for estimating the average number of customers in the bank, for
example. There is an <em>important caveat</em> in using this method. To
estimate the correct time average you must certainly <tt class="docutils literal"><span class="pre">observe</span></tt> the
value (say the number of customers in the system) whenever it changes
(as well as at any other time you wish) but, and this is important,
observing the <em>new</em> value. The <em>old</em> value was recorded earlier. In
practice this means that if we wish to observe a changing value,
<tt class="docutils literal"><span class="pre">n</span></tt>, using the Monitor, <tt class="docutils literal"><span class="pre">Mon</span></tt>, we must keep to the the following
pattern:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">n</span> <span class="o">=</span> <span class="n">n</span><span class="o">+</span><span class="mi">1</span>
<span class="n">Mon</span><span class="o">.</span><span class="n">observe</span><span class="p">(</span><span class="n">n</span><span class="p">,</span><span class="n">now</span><span class="p">())</span>
</pre></div>
</div>
<p>Thus you make the change (not only increases) and <em>then</em> observe the new
value. Of course the simulation time <tt class="docutils literal"><span class="pre">now()</span></tt> has not changed between
the two statements.</p>
<div class="section" id="plotting-a-histogram-of-monitor-results">
<h3>Plotting a Histogram of Monitor results<a class="headerlink" href="#plotting-a-histogram-of-monitor-results" title="Permalink to this headline">¶</a></h3>
<p>A Monitor can construct a histogram from its data using the
<tt class="docutils literal"><span class="pre">histogram</span></tt> method. In this model we monitor the time in the system
for the customers. This is calculated for each customer in line
29, using the arrival time saved in line 19. We create the
Monitor, <tt class="docutils literal"><span class="pre">Mon</span></tt>, at line 37 and the times are <tt class="docutils literal"><span class="pre">observed</span></tt> at line
30.</p>
<p>The histogram is constructed from the Monitor, after the simulation
has finished, at line 55. The SimPy SimPlot package allows
simple plotting of results from simulations. Here we use the SimPlot
<tt class="docutils literal"><span class="pre">plotHistogram</span></tt> method. The plotting routines appear in lines
57-61. The <tt class="docutils literal"><span class="pre">plotHistogram</span></tt> call is in line 58.</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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64</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">"""bank17: Plotting a Histogram of Monitor results"""</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">SimPy.SimPlot</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="n">expovariate</span><span class="p">,</span> <span class="n">seed</span>
<span class="c">## Model components ------------------------</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly"""</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">rate</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">expovariate</span><span class="p">(</span><span class="n">rate</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span>
<span class="c">#print("%8.4f %s: Arrived " % (now(), self.name))</span>
<span class="k">yield</span> <span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="c">#print("%8.4f %s: Got counter " % (now(), self.name))</span>
<span class="n">tib</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">timeInBank</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">tib</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="c">#print("%8.4f %s: Finished " % (now(), self.name))</span>
<span class="n">t</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span> <span class="o">-</span> <span class="n">arrive</span>
<span class="n">Mon</span><span class="o">.</span><span class="n">observe</span><span class="p">(</span><span class="n">t</span><span class="p">)</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">400.0</span> <span class="c"># minutes</span>
<span class="n">counter</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s">"Clerk"</span><span class="p">)</span>
<span class="n">Mon</span> <span class="o">=</span> <span class="n">Monitor</span><span class="p">(</span><span class="s">'Time in the Bank'</span><span class="p">)</span>
<span class="n">N</span> <span class="o">=</span> <span class="mi">0</span>
<span class="c">## Model ----------------------------------</span>
<span class="k">def</span> <span class="nf">model</span><span class="p">(</span><span class="n">SEED</span><span class="o">=</span><span class="mi">393939</span><span class="p">):</span>
<span class="n">seed</span><span class="p">(</span><span class="n">SEED</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">source</span> <span class="o">=</span> <span class="n">Source</span><span class="p">()</span>
<span class="n">activate</span><span class="p">(</span><span class="n">source</span><span class="p">,</span>
<span class="n">source</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="mi">20</span><span class="p">,</span> <span class="n">rate</span><span class="o">=</span><span class="mf">0.1</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
<span class="c">## Experiment ----------------------------------</span>
<span class="n">model</span><span class="p">()</span>
<span class="n">Histo</span> <span class="o">=</span> <span class="n">Mon</span><span class="o">.</span><span class="n">histogram</span><span class="p">(</span><span class="n">low</span><span class="o">=</span><span class="mf">0.0</span><span class="p">,</span> <span class="n">high</span><span class="o">=</span><span class="mf">200.0</span><span class="p">,</span> <span class="n">nbins</span><span class="o">=</span><span class="mi">20</span><span class="p">)</span>
<span class="n">plt</span> <span class="o">=</span> <span class="n">SimPlot</span><span class="p">()</span>
<span class="n">plt</span><span class="o">.</span><span class="n">plotHistogram</span><span class="p">(</span><span class="n">Histo</span><span class="p">,</span> <span class="n">xlab</span><span class="o">=</span><span class="s">'Time (min)'</span><span class="p">,</span>
<span class="n">title</span><span class="o">=</span><span class="s">"Time in the Bank"</span><span class="p">,</span>
<span class="n">color</span><span class="o">=</span><span class="s">"red"</span><span class="p">,</span> <span class="n">width</span><span class="o">=</span><span class="mi">2</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">mainloop</span><span class="p">()</span>
</pre></div>
</td></tr></table></div>
</div>
<div class="section" id="monitoring-a-resource">
<h3>Monitoring a Resource<a class="headerlink" href="#monitoring-a-resource" title="Permalink to this headline">¶</a></h3>
<p>Now consider observing the number of customers waiting or executing in
a Resource. Because of the need to <tt class="docutils literal"><span class="pre">observe</span></tt> the value after the
change but at the same simulation instant, it is impossible to use the
length of the Resource’s <tt class="docutils literal"><span class="pre">waitQ</span></tt> directly with a Monitor defined
outside the Resource. Instead Resources can be set up with built-in
Monitors.</p>
<p>Here is an example using a Monitored Resource. We intend to observe
the average number waiting and active in the <tt class="docutils literal"><span class="pre">counter</span></tt>
resource. <tt class="docutils literal"><span class="pre">counter</span></tt> is defined at line 32 and we have set
<tt class="docutils literal"><span class="pre">monitored=True</span></tt>. This establishes two Monitors: <tt class="docutils literal"><span class="pre">waitMon</span></tt>, to
record changes in the numbers waiting and <tt class="docutils literal"><span class="pre">actMon</span></tt> to record changes
in the numbers active in the <tt class="docutils literal"><span class="pre">counter</span></tt>. We need make no further
change to the operation of the program as monitoring is then
automatic. No <tt class="docutils literal"><span class="pre">observe</span></tt> calls are necessary.</p>
<p>At the end of the run in the <tt class="docutils literal"><span class="pre">model</span></tt> function, we calculate the
<tt class="docutils literal"><span class="pre">timeAverage</span></tt> of both <tt class="docutils literal"><span class="pre">waitMon</span></tt> and <tt class="docutils literal"><span class="pre">actMon</span></tt> and return them
from the <tt class="docutils literal"><span class="pre">model</span></tt> call (line 45). These can then be printed at
the end of the program (line 49).</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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52</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">"""bank15: Monitoring a Resource"""</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="n">expovariate</span><span class="p">,</span> <span class="n">seed</span>
<span class="c">## Model components ------------------------</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly"""</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">rate</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">expovariate</span><span class="p">(</span><span class="n">rate</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Arrived "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Got counter "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="n">tib</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">timeInBank</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">tib</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="k">print</span><span class="p">(</span><span class="s">"</span><span class="si">%8.4f</span><span class="s"> </span><span class="si">%s</span><span class="s">: Finished "</span> <span class="o">%</span> <span class="p">(</span><span class="n">now</span><span class="p">(),</span> <span class="bp">self</span><span class="o">.</span><span class="n">name</span><span class="p">))</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">400.0</span> <span class="c"># minutes</span>
<span class="n">counter</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s">"Clerk"</span><span class="p">,</span> <span class="n">monitored</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="c">## Model ----------------------------------</span>
<span class="k">def</span> <span class="nf">model</span><span class="p">(</span><span class="n">SEED</span><span class="o">=</span><span class="mi">393939</span><span class="p">):</span>
<span class="n">seed</span><span class="p">(</span><span class="n">SEED</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">source</span> <span class="o">=</span> <span class="n">Source</span><span class="p">()</span>
<span class="n">activate</span><span class="p">(</span><span class="n">source</span><span class="p">,</span>
<span class="n">source</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span> <span class="n">rate</span><span class="o">=</span><span class="mf">0.1</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
<span class="k">return</span> <span class="p">(</span><span class="n">counter</span><span class="o">.</span><span class="n">waitMon</span><span class="o">.</span><span class="n">timeAverage</span><span class="p">(),</span> <span class="n">counter</span><span class="o">.</span><span class="n">actMon</span><span class="o">.</span><span class="n">timeAverage</span><span class="p">())</span>
<span class="c">## Experiment ----------------------------------</span>
<span class="k">print</span><span class="p">(</span><span class="s">'Average waiting = </span><span class="si">%6.4f</span><span class="se">\n</span><span class="s">Average active = </span><span class="si">%6.4f</span><span class="se">\n</span><span class="s">'</span> <span class="o">%</span> <span class="n">model</span><span class="p">())</span>
</pre></div>
</td></tr></table></div>
</div>
<div class="section" id="plotting-from-resource-monitors">
<h3>Plotting from Resource Monitors<a class="headerlink" href="#plotting-from-resource-monitors" title="Permalink to this headline">¶</a></h3>
<p>Like all Monitors, <tt class="docutils literal"><span class="pre">waitMon</span></tt> and <tt class="docutils literal"><span class="pre">actMon</span></tt> in a monitored Resource
contain information that enables us to graph the output. Alternative
plotting packages can be used; here we use the simple <tt class="docutils literal"><span class="pre">SimPy.SimPlot</span></tt>
package just to graph the number of customers waiting for the
counter. The program is a simple modification of the one that uses a
monitored Resource.</p>
<p>The SimPlot package is imported at line 3. No major changes are
made to the main part of the program except that I commented out the
print statements. The changes occur in the <tt class="docutils literal"><span class="pre">model</span></tt> routine from lines
37 to 44. The simulation now generates and processes 20
customers (line 43). <tt class="docutils literal"><span class="pre">model</span></tt> does not return a value but the
Monitors of the <tt class="docutils literal"><span class="pre">counter</span></tt> Resource still exist when the simulation has
terminated.</p>
<p>The additional plotting actions take place in lines 50 to
53. Line 51-52 construct a step plot and graphs the
number in the waiting queue as a function of time. <tt class="docutils literal"><span class="pre">waitMon</span></tt> is
primarily a list of <em>[time,value]</em> pairs which the <tt class="docutils literal"><span class="pre">plotStep</span></tt> method
of the SimPlot object, <tt class="docutils literal"><span class="pre">plt</span></tt> uses without change. On running the
program the graph is plotted; the user has to terminate the plotting
<tt class="docutils literal"><span class="pre">mainloop</span></tt> on the screen.</p>
<div class="highlight-python"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
2
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23
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56</pre></div></td><td class="code"><div class="highlight"><pre><span class="sd">"""bank16: Plotting from Resource Monitors"""</span>
<span class="kn">from</span> <span class="nn">SimPy.Simulation</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">SimPy.SimPlot</span> <span class="kn">import</span> <span class="o">*</span>
<span class="kn">from</span> <span class="nn">random</span> <span class="kn">import</span> <span class="n">expovariate</span><span class="p">,</span> <span class="n">seed</span>
<span class="c">## Model components ------------------------</span>
<span class="k">class</span> <span class="nc">Source</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Source generates customers randomly"""</span>
<span class="k">def</span> <span class="nf">generate</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">number</span><span class="p">,</span> <span class="n">rate</span><span class="p">):</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">number</span><span class="p">):</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">Customer</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Customer</span><span class="si">%02d</span><span class="s">"</span> <span class="o">%</span> <span class="p">(</span><span class="n">i</span><span class="p">))</span>
<span class="n">activate</span><span class="p">(</span><span class="n">c</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">visit</span><span class="p">(</span><span class="n">timeInBank</span><span class="o">=</span><span class="mf">12.0</span><span class="p">))</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">expovariate</span><span class="p">(</span><span class="n">rate</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Customer</span><span class="p">(</span><span class="n">Process</span><span class="p">):</span>
<span class="sd">""" Customer arrives, is served and leaves """</span>
<span class="k">def</span> <span class="nf">visit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">timeInBank</span><span class="p">):</span>
<span class="n">arrive</span> <span class="o">=</span> <span class="n">now</span><span class="p">()</span>
<span class="c">#print("%8.4f %s: Arrived " % (now(), self.name))</span>
<span class="k">yield</span> <span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="c">#print("%8.4f %s: Got counter " % (now(), self.name))</span>
<span class="n">tib</span> <span class="o">=</span> <span class="n">expovariate</span><span class="p">(</span><span class="mf">1.0</span> <span class="o">/</span> <span class="n">timeInBank</span><span class="p">)</span>
<span class="k">yield</span> <span class="n">hold</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">tib</span>
<span class="k">yield</span> <span class="n">release</span><span class="p">,</span> <span class="bp">self</span><span class="p">,</span> <span class="n">counter</span>
<span class="c">#print("%8.4f %s: Finished " % (now(), self.name))</span>
<span class="c">## Experiment data -------------------------</span>
<span class="n">maxTime</span> <span class="o">=</span> <span class="mf">400.0</span> <span class="c"># minutes</span>
<span class="n">counter</span> <span class="o">=</span> <span class="n">Resource</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s">"Clerk"</span><span class="p">,</span> <span class="n">monitored</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="c">## Model -----------------------------------</span>
<span class="k">def</span> <span class="nf">model</span><span class="p">(</span><span class="n">SEED</span><span class="o">=</span><span class="mi">393939</span><span class="p">):</span>
<span class="n">seed</span><span class="p">(</span><span class="n">SEED</span><span class="p">)</span>
<span class="n">initialize</span><span class="p">()</span>
<span class="n">source</span> <span class="o">=</span> <span class="n">Source</span><span class="p">()</span>
<span class="n">activate</span><span class="p">(</span><span class="n">source</span><span class="p">,</span>
<span class="n">source</span><span class="o">.</span><span class="n">generate</span><span class="p">(</span><span class="n">number</span><span class="o">=</span><span class="mi">20</span><span class="p">,</span> <span class="n">rate</span><span class="o">=</span><span class="mf">0.1</span><span class="p">),</span> <span class="n">at</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="n">simulate</span><span class="p">(</span><span class="n">until</span><span class="o">=</span><span class="n">maxTime</span><span class="p">)</span>
<span class="c">## Experiment -----------------------------------</span>
<span class="n">model</span><span class="p">()</span>
<span class="n">plt</span> <span class="o">=</span> <span class="n">SimPlot</span><span class="p">()</span>
<span class="n">plt</span><span class="o">.</span><span class="n">plotStep</span><span class="p">(</span><span class="n">counter</span><span class="o">.</span><span class="n">waitMon</span><span class="p">,</span>
<span class="n">color</span><span class="o">=</span><span class="s">"red"</span><span class="p">,</span> <span class="n">width</span><span class="o">=</span><span class="mi">2</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">mainloop</span><span class="p">()</span>
</pre></div>
</td></tr></table></div>
</div>
</div>
<div class="section" id="acknowledgements">
<h2>Acknowledgements<a class="headerlink" href="#acknowledgements" title="Permalink to this headline">¶</a></h2>
<p>I thank Klaus Muller, Bob Helmbold, Mukhlis Matti and the other
developers and users of SimPy for improving this document by sending
their comments. I would be grateful for any further corrections or
suggestions. Please send them to: <em>vignaux</em> at
<em>users.sourceforge.net</em>.</p>
</div>
<div class="section" id="references">
<h2>References<a class="headerlink" href="#references" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li>Python website: <a class="reference external" href="http://www.Python.org">http://www.Python.org</a></li>
<li>SimPy homepage: <a class="reference external" href="http://simpy.sourceforge.net/">http://simpy.sourceforge.net/</a></li>
<li>The Bank:</li>
</ul>
</div>
</div>
</div>
</div>
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<h3><a href="../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">The Bank Tutorial part 2: More examples of SimPy Simulation</a><ul>
<li><a class="reference internal" href="#introduction">Introduction</a></li>
<li><a class="reference internal" href="#priority-customers">Priority Customers</a><ul>
<li><a class="reference internal" href="#priority-customers-without-preemption">Priority Customers without preemption</a></li>
<li><a class="reference internal" href="#priority-customers-with-preemption">Priority Customers with preemption</a></li>
</ul>
</li>
<li><a class="reference internal" href="#balking-and-reneging-customers">Balking and Reneging Customers</a><ul>
<li><a class="reference internal" href="#balking-customers">Balking Customers</a></li>
<li><a class="reference internal" href="#reneging-or-abandoning-customers">Reneging (or abandoning) Customers</a></li>
</ul>
</li>
<li><a class="reference internal" href="#processes">Processes</a><ul>
<li><a class="reference internal" href="#interrupting-a-process">Interrupting a Process.</a></li>
<li><a class="reference internal" href="#waituntil-the-bank-door-opens"><tt class="docutils literal"><span class="pre">waituntil</span></tt> the Bank door opens</a></li>
<li><a class="reference internal" href="#wait-for-the-doorman-to-give-a-signal-waitevent">Wait for the doorman to give a signal: <tt class="docutils literal"><span class="pre">waitevent</span></tt></a></li>
</ul>
</li>
<li><a class="reference internal" href="#monitors">Monitors</a><ul>
<li><a class="reference internal" href="#plotting-a-histogram-of-monitor-results">Plotting a Histogram of Monitor results</a></li>
<li><a class="reference internal" href="#monitoring-a-resource">Monitoring a Resource</a></li>
<li><a class="reference internal" href="#plotting-from-resource-monitors">Plotting from Resource Monitors</a></li>
</ul>
</li>
<li><a class="reference internal" href="#acknowledgements">Acknowledgements</a></li>
<li><a class="reference internal" href="#references">References</a></li>
</ul>
</li>
</ul>
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