From d3717bdf8f08a0e1039158c8bab2c24d20f492b6 Mon Sep 17 00:00:00 2001 From: keios Date: Tue, 3 Oct 2006 01:13:49 -0700 Subject: [PATCH] [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 --- lib/sort.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/lib/sort.c b/lib/sort.c index 5f3b51ffa1dc..488788b341cb 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) -- 2.20.1