From: keios Date: Tue, 3 Oct 2006 08:13:49 +0000 (-0700) Subject: [PATCH] low performance of lib/sort.c X-Git-Tag: v2.6.19-rc1~361 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d3717bdf8f08a0e1039158c8bab2c24d20f492b6;p=linux-2.6 [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: keios Acked-by: Matt Mackall Acked-by: Zou Nan hai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/lib/sort.c b/lib/sort.c index 5f3b51ffa1..488788b341 100644 --- a/lib/sort.c +++ b/lib/sort.c @@ -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)