git/compat at ee4f06c0a60d8b17efdd8f6a3332f175f6aafe0e - git

Tree: ee4f06c0a6

Brian Downing 43fe901b71 compat: Add simplified merge sort implementation from glibc qsort in Windows 2000 (and various other C libraries) is a Quicksort with the usual O(n^2) worst case. Unfortunately, sorting Git trees seems to get very close to that worst case quite often: $ /git/gitbad runstatus # On branch master qsort, nmemb = 30842 done, 237838087 comparisons. This patch adds a simplified version of the merge sort that is glibc's qsort(3). As a merge sort, this needs a temporary array equal in size to the array that is to be sorted, but has a worst-case performance of O(n log n). The complexity that was removed is: * Doing direct stores for word-size and -aligned data. * Falling back to quicksort if the allocation required to perform the merge sort would likely push the machine into swap. Even with these simplifications, this seems to outperform the Windows qsort(3) implementation, even in Windows XP (where it is "fixed" and doesn't trigger O(n^2) complexity on trees). [jes: moved into compat/qsort.c, as per Johannes Sixt's suggestion] [bcd: removed gcc-ism, thanks to Edgar Toernig. renamed make variable per Junio's comment.] Signed-off-by: Brian Downing <bdowning@lavos.net> Signed-off-by: Steffen Prohaska <prohaska@zib.de> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>		17 years ago
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hstrerror.c	…
inet_ntop.c	…
inet_pton.c	…
memmem.c	…
mkdtemp.c	…
mmap.c	…
pread.c	…
qsort.c	compat: Add simplified merge sort implementation from glibc	17 years ago
setenv.c	…
strcasestr.c	…
strlcpy.c	…
strtoumax.c	…
unsetenv.c	…