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* add qsort_r and make qsort a wrapper around itÉrico Nogueira2021-09-231-17/+20
| | | | | | | | | | | | | we make qsort a wrapper by providing a wrapper_cmp function that uses the extra argument as a function pointer. should be optimized to a tail call on most architectures, as long as it's built with -fomit-frame-pointer, so the performance impact should be minimal. to keep the git history clean, for now qsort_r is implemented in qsort.c and qsort is implemented in qsort_nr.c. qsort.c also received a few trivial cleanups, including replacing (*cmp)() calls with cmp(). qsort_nr.c contains only wrapper_cmp and qsort as a qsort_r wrapper itself.
* qsort: add a short comment about the algorithmLeah Neukirchen2017-08-111-0/+3
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* avoid crashing when nel==0 is passed to qsortRich Felker2011-04-291-2/+6
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* replace heap sort with smoothsort implementation by Valentin OchsRich Felker2011-04-271-32/+193
| | | | | | | | | | | | | | Smoothsort is an adaptive variant of heapsort. This version was written by Valentin Ochs (apo) specifically for inclusion in musl. I worked with him to get it working in O(1) memory usage even with giant array element widths, and to optimize it heavily for size and speed. It's still roughly 4 times as large as the old heap sort implementation, but roughly 20 times faster given an almost-sorted array of 1M elements (20 being the base-2 log of 1M), i.e. it really does reduce O(n log n) to O(n) in the mostly-sorted case. It's still somewhat slower than glibc's Introsort for random input, but now considerably faster than glibc when the input is already sorted, or mostly sorted.
* don't compare elements with themselves during qsort.Rich Felker2011-02-171-1/+1
| | | | | this is actually a workaround for a bug in gcc, whereby it asserts inequality of the keys being compared...
* initial check-in, version 0.5.0 v0.5.0Rich Felker2011-02-121-0/+50