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Commit d3717bdf authored by keios's avatar keios Committed by Linus Torvalds
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[PATCH] low performance of lib/sort.c 



It is a non-standard heap-sort algorithm implementation because the index
of child node is wrong .  The sort function still outputs right result, but
the performance is O( n * ( log(n) + 1 ) ) , about 10% ~ 20% worse than
standard algorithm.

Signed-off-by: default avatarkeios <keios.cn@gmail.com>
Acked-by: default avatarMatt Mackall <mpm@selenic.com>
Acked-by: default avatarZou Nan hai <nanhai.zou@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ffc50891

lib/sort.c

+5 −5
Original line number Diff line number Diff line
@@ -49,15 +49,15 @@ void sort(void *base, size_t num, size_t size, 
	  void (*swap)(void *, void *, int size))

{

	/* pre-scale counters for performance */

	int i = (num/2) * size, n = num * size, c, r;

	int i = (num/2 - 1) * size, n = num * size, c, r;



	if (!swap)

		swap = (size == 4 ? u32_swap : generic_swap);



	/* heapify */

	for ( ; i >= 0; i -= size) {

		for (r = i; r * 2 < n; r  = c) {

			c = r * 2;

		for (r = i; r * 2 + size < n; r  = c) {

			c = r * 2 + size;

			if (c < n - size && cmp(base + c, base + c + size) < 0)

				c += size;

			if (cmp(base + r, base + c) >= 0)
@@ -69,8 +69,8 @@ void sort(void *base, size_t num, size_t size, 
	/* sort */

	for (i = n - size; i >= 0; i -= size) {

		swap(base, base + i, size);

		for (r = 0; r * 2 < i; r = c) {

			c = r * 2;

		for (r = 0; r * 2 + size < i; r = c) {

			c = r * 2 + size;

			if (c < i - size && cmp(base + c, base + c + size) < 0)

				c += size;

			if (cmp(base + r, base + c) >= 0)