Re: absurdly slow git-diff
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: 2016-06-15 22:45:37
Subsystem:
the rest · Maintainer:
Linus Torvalds
On Fri, 7 Nov 2008, Davide Libenzi wrote:
With +/- 100 lines (200 lines window): davide@alien:~$ time ./xdiff_test --diff 1 2 > /dev/null real 0m1.534s user 0m1.466s sys 0m0.040s
I assume the patch is something like the appended? Linus --- xdiff/xprepare.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/xdiff/xprepare.c b/xdiff/xprepare.c
index e87ab57..4bebd76 100644
--- a/xdiff/xprepare.c
+++ b/xdiff/xprepare.c@@ -318,7 +318,7 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) { * Note that we always call this function with dis[i] > 1, so the * current line (i) is already a multimatch line. */ - for (r = 1, rdis0 = 0, rpdis0 = 1; (i - r) >= s; r++) { + for (r = 1, rdis0 = 0, rpdis0 = 1; r < 100 && (i - r) >= s; r++) { if (!dis[i - r]) rdis0++; else if (dis[i - r] == 2)
@@ -334,7 +334,7 @@ static int xdl_clean_mmatch(char const *dis, long i, long s, long e) { */ if (rdis0 == 0) return 0; - for (r = 1, rdis1 = 0, rpdis1 = 1; (i + r) <= e; r++) { + for (r = 1, rdis1 = 0, rpdis1 = 1; r < 100 && (i + r) <= e; r++) { if (!dis[i + r]) rdis1++; else if (dis[i + r] == 2)