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From: "chri.snell at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/55169] New: std::discrete_distribution::operator(generator&) makes unnecessary copy of parameter vector
Date: Thu, 01 Nov 2012 19:34:00 -0000	[thread overview]
Message-ID: <bug-55169-4@http.gcc.gnu.org/bugzilla/> (raw)


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55169

             Bug #: 55169
           Summary: std::discrete_distribution::operator(generator&) makes
                    unnecessary copy of parameter vector
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: chri.snell@gmail.com


Created attachment 28592
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28592
demonstration of slow std::discrete_distribution in GCC

std::discrete_distribution::operator()(generator&) is significantly slower than
directly calling operator()(generator&, const param_type&), which it delegates
to.  This is because, on random.h:4805, this->param() returns a copy rather
than a const reference.

The attached file is a simple test demonstrating this inefficient behaviour.


             reply	other threads:[~2012-11-01 19:34 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-11-01 19:34 chri.snell at gmail dot com [this message]
2012-11-01 19:39 ` [Bug libstdc++/55169] " paolo.carlini at oracle dot com
2012-11-01 19:48 ` chri.snell at gmail dot com
2012-11-01 20:00 ` paolo.carlini at oracle dot com
2012-11-02 10:46 ` paolo at gcc dot gnu.org
2012-11-02 11:18 ` paolo at gcc dot gnu.org
2012-11-02 11:20 ` paolo.carlini at oracle dot com

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