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Re: The Performance Elephant is Dead

From: Peter Samuelson <peter_at_p12n.org>
Date: Wed, 7 Jul 2010 10:02:36 -0500

[Stefan Fuhrmann]
> * zlib: major deflate() and adler32() speedup, minor inflate() speedup

What is the story with the s->level > 0 thing in deflate.c? I note
that you slide the hash table only if s->level > 0, but the comment
right above this states:

            /* Slide the hash table (could be avoided with 32 bit values
               at the expense of memory usage). We slide even when level == 0
               to keep the hash table consistent if we switch back to level > 0
               later. (Using level 0 permanently is not an optimal usage of
               zlib, so we don't care about this pathological case.)

From this comment, it looks like adding your "if (s->level > 0)" adds a
bug. The only time it would work properly is if you use what they call
"this pathological case", which Subversion does not.

Peter Samuelson | org-tld!p12n!peter | http://p12n.org/
Received on 2010-07-07 17:04:15 CEST

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