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<ul id="index">
  <li><a href="#NAME">NAME</a></li>
  <li><a href="#Description">Description</a></li>
  <li><a href="#backticks-vs-XS">backticks vs XS</a></li>
  <li><a href="#sv_catpvn-vs.-fprintf">sv_catpvn vs. fprintf</a></li>
  <li><a href="#Maintainers">Maintainers</a></li>
  <li><a href="#Authors">Authors</a></li>
</ul>

<h1 id="NAME">NAME</h1>

<p>Which Coding Technique is Faster</p>

<h1 id="Description">Description</h1>

<p>This document tries to show more efficient coding styles by benchmarking various styles.</p>

<p>WARNING: This doc is under construction</p>

<p>META: for now these are just unprocessed snippets from the mailing list. Please help me to make these into useful essays.</p>

<h1 id="backticks-vs-XS">backticks vs XS</h1>

<p>META: unprocessed yet.</p>

<p>compare the difference of calling an xsub that does _nothing_ vs. a backticked program that does _nothing_.</p>

<pre><code>  /* file:test.c */
  int main(int argc, char **argv, char **env)
  {
      return 1;
  }

  /* file:TickTest.xs */
  #include &quot;EXTERN.h&quot;
  #include &quot;perl.h&quot;
  #include &quot;XSUB.h&quot;
  
  MODULE = TickTest             PACKAGE = TickTest              
  
  void
  foo()
  
  CODE:

  # file:test.pl
  use blib;
  use TickTest ();
  
  use Benchmark;
  
  timethese(100_000, {
      backtick =&gt; sub { `./test` },
      xs =&gt; sub { TickTest::foo() },
  });</code></pre>

<p>Results:</p>

<pre><code>  Benchmark: timing 100000 iterations of backtick, xs...
    backtick: 292 wallclock secs (18.68 usr 43.93 sys + 142.43 cusr 84.00 csys = 289.04 CPU) @ 1597.19/s (n=100000)
          xs: -1 wallclock secs ( 0.25 usr +  0.00 sys =  0.25 CPU) @ 400000.00/s (n=100000)
              (warning: too few iterations for a reliable count)</code></pre>

<h1 id="sv_catpvn-vs.-fprintf">sv_catpvn vs. fprintf</h1>

<p>META: unprocessed yet.</p>

<p>and what i&#39;m trying to say is that if both the xs code and external program are doing the same thing, xs will be heaps faster than backticking a program. your xsub and external program are not doing the same thing.</p>

<p>i&#39;m guessing part of the difference in your code is due to fprintf having a pre-allocated buffer, whereas the SV&#39;s SvPVX has not been pre-allocated and gets realloc-ed each time you call sv_catpv. have a look at the code below, fprintf is faster than sv_catpvn, but if the SvPVX is preallocated, sv_catpvn becomes faster than fprintf:</p>

<pre><code>  timethese(1_000, {
      fprintf   =&gt; sub { TickTest::fprintf() },
      svcat     =&gt; sub { TickTest::svcat() },
      svcat_pre =&gt; sub { TickTest::svcat_pre() },
  });
  
  Benchmark: timing 1000 iterations of fprintf, svcat, svcat_pre...
     fprintf:  9 wallclock secs ( 8.72 usr +  0.00 sys =  8.72 CPU) @ 114.68/s (n=1000)
       svcat: 13 wallclock secs (12.82 usr +  0.00 sys = 12.82 CPU) @ 78.00/s (n=1000)
   svcat_pre:  2 wallclock secs ( 2.75 usr +  0.00 sys =  2.75 CPU) @ 363.64/s (n=1000)
  
  #include &quot;EXTERN.h&quot;
  #include &quot;perl.h&quot;
  #include &quot;XSUB.h&quot;
  
  static FILE *devnull;
  
  MODULE = TickTest             PACKAGE = TickTest              
  
  BOOT:
  devnull = fopen(&quot;/dev/null&quot;, &quot;w&quot;);
  
  void
  fprintf()
  
      CODE:
      {
          int i;
          char buffer[8292];
  
          for (i=0; i&lt;sizeof(buffer); i++) {
              fprintf(devnull, &quot;a&quot;);
          }
      }
  
  void
  svcat()
  
      CODE:
      {
          int i;
          char buffer[8292];
          SV *sv = newSV(0);
  
          for (i=0; i&lt;sizeof(buffer); i++) {
              sv_catpvn(sv, &quot;a&quot;, 1);
          }
  
          SvREFCNT_dec(sv);
      }
  
  void
  svcat_pre()
  
      CODE:
      {
          int i;
          char buffer[8292];
          SV *sv = newSV(sizeof(buffer)+1);
  
          for (i=0; i&lt;sizeof(buffer); i++) {
              sv_catpvn(sv, &quot;a&quot;, 1);
          }
  
          SvREFCNT_dec(sv);
      }</code></pre>

<h1 id="Maintainers">Maintainers</h1>

<p>Maintainer is the person(s) you should contact with updates, corrections and patches.</p>

<p>Stas Bekman [http://stason.org/]</p>

<h1 id="Authors">Authors</h1>

<ul>

<li><p>Stas Bekman [http://stason.org/]</p>

</li>
<li><p>Doug MacEachern &lt;dougm (at) covalent.net&gt;</p>

</li>
</ul>

<p>Only the major authors are listed above. For contributors see the Changes file.</p>


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