Re: [PATCH 3/4] diffcore-pickaxe: further refactor count_match()

Junio C Hamano schrieb:

René Scharfe [off-list ref] writes:

quoted

I get this (Ubuntu 8.10 x64, Fedora 10 x64 using the same Linux repo,
Windows Vista x64 using a different Linux repo with the same HEAD on
NTFS and msysgit, numbers are the elapsed time in seconds, best of five
runs):

                           Ubuntu  Fedora  Windows
   v1.6.2-rc2                8.14    8.16    9.236
   v1.6.2-rc2+[1-4]          2.43    2.45    2.995
   v1.6.2-rc2+[1-4]+memmem   1.31    1.25    2.917
   v1.6.2-rc2+[1-3]+memmem   1.51    1.16    8.455

Ubuntu has glibc 2.8, while Fedora 10 has glibc 2.9, with a new and more
efficient memmem() implementation.  On Windows, we use our own naive
memmem() implementation.

Yeah, what does glibc use these days?  Some variant of Boyer-Moore?

No, the algorithm is called Two Way, which, unlike Boyer-Moore, only
needs constant space.  The implementation seems to originate from this bug:

	http://sourceware.org/bugzilla/show_bug.cgi?id=5514

And the algorithm is documented here:

	http://www-igm.univ-mlv.fr/~lecroq/string/node26.html

René