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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<a name="Is-backing-up-a-big-deal_003f"></a>
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<p>
Next: <a href="Can-I-fake-multi_002dbyte-character-support_003f.html#Can-I-fake-multi_002dbyte-character-support_003f" accesskey="n" rel="next">Can I fake multi-byte character support?</a>, Previous: <a href="Are-certain-equivalent-patterns-faster-than-others_003f.html#Are-certain-equivalent-patterns-faster-than-others_003f" accesskey="p" rel="prev">Are certain equivalent patterns faster than others?</a>, Up: <a href="FAQ.html#FAQ" accesskey="u" rel="up">FAQ</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p>
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<a name="Is-backing-up-a-big-deal_003f-1"></a>
<h3 class="unnumberedsec">Is backing up a big deal?</h3>
<div class="example">
<pre class="verbatim">To: Adoram Rogel &lt;adoram@hybridge.com&gt;
Subject: Re: Flex 2.5.2 performance questions
In-reply-to: Your message of Thu, 19 Sep 96 10:16:04 EDT.
Date: Thu, 19 Sep 96 09:58:00 PDT
From: Vern Paxson &lt;vern&gt;

&gt; a lot about the backing up problem.
&gt; I believe that there lies my biggest problem, and I'll try to improve
&gt; it.

Since you have variable trailing context, this is a bigger performance
problem.  Fixing it is usually easier than fixing backing up, which in a
complicated scanner (yours seems to fit the bill) can be extremely
difficult to do correctly.

You also don't mention what flags you are using for your scanner.
-f makes a large speed difference, and -Cfe buys you nearly as much
speed but the resulting scanner is considerably smaller.

&gt; I have an | operator in {and} and in {pats} so both of them are variable
&gt; length.

-p should have reported this.

&gt; Is changing one of them to fixed-length is enough ?

Yes.

&gt; Is it possible to change the 32,000 states limit ?

Yes.  I've appended instructions on how.  Before you make this change,
though, you should think about whether there are ways to fundamentally
simplify your scanner - those are certainly preferable!

		Vern

To increase the 32K limit (on a machine with 32 bit integers), you increase
the magnitude of the following in flexdef.h:

#define JAMSTATE -32766 /* marks a reference to the state that always jams */
#define MAXIMUM_MNS 31999
#define BAD_SUBSCRIPT -32767
#define MAX_SHORT 32700

Adding a 0 or two after each should do the trick.
</pre></div>

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