Messages in this thread Patch in this message | | | Date | Thu, 28 Sep 2006 23:18:45 +0800 | From | keios <> | Subject | [PATCH] low performance of lib/sort.c , kernel 2.6.18 |
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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: keios <keios.cn@gmail.com> ----- diff -Nraup a/lib/sort.c b/lib/sort.c --- a/lib/sort.c 2006-09-20 11:42:06.000000000 +0800 +++ b/lib/sort.c 2006-09-27 21:26:38.000000000 +0800 @@ -49,15 +49,15 @@ void sort(void *base, size_t num, size_t 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 /* 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) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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