patchgrep - Patches: patch #3802, Red Hat's "dfa-optional"...

 
 

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patch #3802: Red Hat's "dfa-optional" patch

Submitter:  Charles Levert <charles_levert>
Submitted:  Tue 08 Mar 2005 12:03:26 PM UTC
   
 
Category:  None Priority:  5 - Normal
Status:  Wont Do Privacy:  Public
Assigned to:  None Open/Closed:  Closed

Mon 08 Mar 2010 04:51:02 PM UTC, comment #4: 

The fuller story is that the DFA can be optimized to do better than the glibc regex matcher.

Paolo Bonzini <bonzini>
  Spam posted by anonymous
Thu 28 Apr 2005 12:13:27 PM UTC, comment #2: 

The full story with this patch is that the grep built-in DFA actually pessimises rather than optimises when processing UTF-8.  The idea of this patch is: if we are using UTF-8, disable grep's built-in DFA altogether.

(The DFA in glibc handles UTF-8 correctly, and fast.)

Tim Waugh <twaugh>
Thu 28 Apr 2005 11:49:25 AM UTC, comment #1: 

Tim Waugh wrote of grep-2.5.1-gofast.patch (patch #3478), from which this patch is derived, "I wrote this to partially address bug #69900 (grep writing output very slow): https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=69900 ".

Julian Foad <julianfoad>
Tue 08 Mar 2005 12:03:26 PM UTC, original submission:  

This item is created to document in Savannah the existence of the following patch from Red Hat/Fedora:
  <http://cvs.fedora.redhat.com/viewcvs/devel/grep/>
  :pserver:anonymous@cvs.fedora.redhat.com:/cvs/dist
  grep-2.5.1-dfa-optional.patch

Here is the relevant log content:
  * Fri Jan  7 2005 Tim Waugh <twaugh@redhat.com>
  - Cache MB_CUR_MAX value in egf-speedup patch.
  * Thu Nov 18 2004 Tim Waugh <twaugh@redhat.com> 2.5.1-40
  - Fixed a bug in the fgrep patch, exposed by the dfa-optional patch (bug #138558).
  * Wed Nov 10 2004 Tim Waugh <twaugh@redhat.com>
  - Prevent false matches when DFA is disabled (bug #138558).
  * Mon Nov  8 2004 Tim Waugh <twaugh@redhat.com> 2.5.1-36
  - Automatically disable DFA when processing multibyte input.  GREP_USE_DFA environment variable overrides.
  * Fri Nov  5 2004 Tim Waugh <twaugh@redhat.com> 2.5.1-35
  - Fixes to egf-speedup patch: now it does not change any functionality, as intended.
  - GREP_NO_DFA now turns off the DFA engine, for performance testing.

Charles Levert <charles_levert>

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

No files currently attached

 

Depends on the following items: None found

Items that depend on this one: None found

 

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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2010-03-08 bonzini StatusNone Wont Do
        Open/ClosedOpen Closed

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