(flex.info)Is backing up a big deal?

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Is backing up a big deal?
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     To: Adoram Rogel <adoram@hybridge.com>
     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 <vern>
     
     > a lot about the backing up problem.
     > I believe that there lies my biggest problem, and I'll try to improve
     > 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.
     
     > I have an | operator in {and} and in {pats} so both of them are variable
     > length.
     
     -p should have reported this.
     
     > Is changing one of them to fixed-length is enough ?
     
     Yes.
     
     > 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.