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Re: [patch, libstdc++] std::shuffle: Generate two swap positions at a time if possible

From: Eelis <eelis at eelis dot net>
Cc: libstdc++ <libstdc++ at gcc dot gnu dot org>, gcc-patches <gcc-patches at gcc dot gnu dot org>
Date: Wed, 25 May 2016 19:12:59 +0200
Subject: Re: [patch, libstdc++] std::shuffle: Generate two swap positions at a time if possible
Authentication-results: sourceware.org; auth=none
Newsgroups: gmane.comp.gcc.patches
References: <ng536o$4iu$1 at ger dot gmane dot org> <ng53cl$4iu$2 at ger dot gmane dot org> <CAH6eHdTnASg7A5USA_sTAHXPfUFmkrZvF27tZUJhj5ywwDVDag at mail dot gmail dot com> <5728B8CC dot 7030405 at eelis dot net>

On 2016-05-01 16:18, Eelis wrote:

The attached patch optimizes std::shuffle for the very common case
where the generator range is large enough that a single invocation
can produce two swap positions.

This reduces the runtime of the following testcase by 37% on my machine:


Gentle ping. :)  Did anyone get a chance to take a look at this?

Does the idea seem sound? Does the implementation seem correct?

Thanks,

Eelis

References:
- Re: [patch, libstdc++] std::shuffle: Generate two swap positions at a time if possible
  - From: Eelis
- Re: [patch, libstdc++] std::shuffle: Generate two swap positions at a time if possible
  - From: Jonathan Wakely
- Re: [patch, libstdc++] std::shuffle: Generate two swap positions at a time if possible
  - From: Eelis van der Weegen

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