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This is a patched version of zlib, modified to use Pentium-Pro-optimized assembly code in the deflation algorithm. The files changed/added by this patch are: README.686 match.S The speedup that this patch provides varies, depending on whether the compiler used to build the original version of zlib falls afoul of the PPro's speed traps. My own tests show a speedup of around 10-20% at the default compression level, and 20-30% using -9, against a version compiled using gcc 2.7.2.3. Your mileage may vary. Note that this code has been tailored for the PPro/PII in particular, and will not perform particuarly well on a Pentium. If you are using an assembler other than GNU as, you will have to translate match.S to use your assembler's syntax. (Have fun.) Brian Raiter breadbox@muppetlabs.com April, 1998 Added for zlib 1.1.3: The patches come from http://www.muppetlabs.com/~breadbox/software/assembly.html To compile zlib with this asm file, copy match.S to the zlib directory then do: CFLAGS="-O3 -DASMV" ./configure make OBJA=match.o Update: I've been ignoring these assembly routines for years, believing that gcc's generated code had caught up with it sometime around gcc 2.95 and the major rearchitecting of the Pentium 4. However, I recently learned that, despite what I believed, this code still has some life in it. On the Pentium 4 and AMD64 chips, it continues to run about 8% faster than the code produced by gcc 4.1. In acknowledgement of its continuing usefulness, I've altered the license to match that of the rest of zlib. Share and Enjoy! Brian Raiter breadbox@muppetlabs.com April, 2007