From: Davide Libenzi <davidel@xmailserver.org>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Junio C Hamano <junkio@cox.net>,
git@vger.kernel.org, Jim Meyering <jim@meyering.net>
Subject: Re: git-diff-tree inordinately (O(M*N)) slow on files with many changes
Date: Mon, 16 Oct 2006 16:52:00 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0610161651010.7697@alien.or.mcafeemobile.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0610161604360.3962@g5.osdl.org>
On Mon, 16 Oct 2006, Linus Torvalds wrote:
> That said, it unnecessarily calculates "BITS_IN_LONG - (b)" to shift with,
> because it really shouldn't matter _which_ high bits you use for hashing,
> so you might as well just use the "next" b bits, and have
>
> #define XDL_ADDBITS(v,b) ((v) + ((v) >> (b)))
> #define XDL_MASKBITS(b) ((1UL << (b)) - 1)
> #define XDL_HASHLONG(v,b) (XDL_ADDBITS((unsigned long)(v), b) & XDL_MASKBITS(b))
Ok, I'm fine with this. And my Opteron agrees too:
real 0m0.283s
user 0m0.267s
sys 0m0.016s
- Davide
next prev parent reply other threads:[~2006-10-16 23:52 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-16 14:12 git-diff-tree inordinately (O(M*N)) slow on files with many changes Jim Meyering
2006-10-16 15:47 ` Linus Torvalds
2006-10-16 16:12 ` Linus Torvalds
2006-10-16 16:33 ` Jim Meyering
2006-10-16 16:42 ` Davide Libenzi
2006-10-16 16:50 ` Jim Meyering
2006-10-16 16:54 ` Davide Libenzi
2006-10-16 16:57 ` Jim Meyering
2006-10-16 17:02 ` Davide Libenzi
2006-10-16 17:56 ` Linus Torvalds
2006-10-16 18:03 ` Linus Torvalds
2006-10-16 18:41 ` Davide Libenzi
2006-10-16 18:18 ` Davide Libenzi
2006-10-16 18:51 ` Linus Torvalds
2006-10-16 19:44 ` Davide Libenzi
2006-10-16 20:29 ` Jakub Narebski
2006-10-16 22:53 ` Junio C Hamano
2006-10-16 23:24 ` Linus Torvalds
2006-10-16 23:52 ` Davide Libenzi [this message]
2006-10-16 18:24 ` Jim Meyering
2006-10-16 18:30 ` Davide Libenzi
2006-10-16 18:43 ` Jim Meyering
2006-10-16 16:54 ` Linus Torvalds
2006-10-16 16:36 ` Davide Libenzi
2006-10-16 16:57 ` Linus Torvalds
2006-10-16 16:24 ` Davide Libenzi
2006-10-16 16:54 ` Jakub Narebski
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