From: Thomas Rast <trast@student.ethz.ch>
Date: Sat, 20 Feb 2010 13:38:29 GMT
Subject: Re: [PATCH] rebase -i: avoid --cherry-pick when rebasing to a direct ancestor
Message-ID: <201002201438.29635.trast@student.ethz.ch>
In-Reply-To: <20100220072728.GA12168@coredump.intra.peff.net>

On Saturday 20 February 2010 08:27:28 Jeff King wrote:
> But it is probably the source of the slowness to xdiff that
> gigantic files.

BTW, here's a weird data point:

$ ls -l a b
-rw-r--r-- 1 thomas users 3300765 2010-02-20 12:48 a
-rw-r--r-- 1 thomas users 3253762 2010-02-20 12:48 b
$ time diff -u a b | wc -l
54530

real    0m0.644s
user    0m0.562s
sys     0m0.044s
$ time git diff --no-index a b >/dev/null

real    0m22.848s
user    0m21.956s
sys     0m0.137s
$ time git diff --no-index --patience a b >/dev/null

real    0m19.508s
user    0m18.673s
sys     0m0.273s

'a' and 'b' are two pnm's as per the OPs specification, I made 'a' a
gradient and 'b' the same with two crosses drawn over it.  You can
find them at

  http://thomasrast.ch/download/slow-diff-pnms.zip

if you want to reproduce.

So what on earth does 'diff' do that makes it 35 times as fast?

-- 
Thomas Rast
trast@{inf,student}.ethz.ch