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Optimize bsearch() implementation for performance

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Optimize the bsearch() function to improve binary search performance.
Although the code size grew by 8 bytes, the new implementation achieves
a 15% reduction in execution time on my x86 machine, according to the
bench-bsearch benchmark results.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: DJ Delorie <dj@redhat.com>
This commit is contained in:
Kuan-Wei Chiu 2024-09-10 00:23:27 +08:00 committed by DJ Delorie
parent dce846c789
commit 950891b5e7
1 changed files with 9 additions and 11 deletions
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20
bits/stdlib-bsearch.h
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@ -20,22 +20,14 @@ __extern_inline void *
bsearch (const void *__key, const void *__base, size_t __nmemb, size_t __size,
__compar_fn_t __compar)
{
size_t __l, __u, __idx;
const void *__p;
int __comparison;
__l = 0;
__u = __nmemb;
while (__l < __u)
while (__nmemb)
{
__idx = (__l + __u) / 2;
__p = (const void *) (((const char *) __base) + (__idx * __size));
__p = (const void *) (((const char *) __base) + ((__nmemb >> 1) * __size));
__comparison = (*__compar) (__key, __p);
if (__comparison < 0)
__u = __idx;
else if (__comparison > 0)
__l = __idx + 1;
else
if (__comparison == 0)
{
#if __GNUC_PREREQ(4, 6)
# pragma GCC diagnostic push
@ -46,6 +38,12 @@ bsearch (const void *__key, const void *__base, size_t __nmemb, size_t __size,
# pragma GCC diagnostic pop
#endif
}
if (__comparison > 0)
{
__base = ((const char *) __p) + __size;
--__nmemb;
}
__nmemb >>= 1;
}
return NULL;