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Re: 2.5X slowdown with g++ 3.4 (probably 3.3 also) over 3.2
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From: |
P Ruetz |
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Subject: |
Re: 2.5X slowdown with g++ 3.4 (probably 3.3 also) over 3.2 |
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Date: |
Sun, 25 Sep 2005 17:05:23 GMT |
"P Ruetz" <parmailbox-news@yahoo.com> wrote in message
news:9SzYe.1088$xc4.88@newssvr13.news.prodigy.com...
>I hope this issue has not been discussed before. My search on this topic
> did not turn up anything pertinent.
>
> I have been compiling a computationally bound C++ program with MS Visual
> C++
> and various GNU g++ versions for some time.
>
> Normally, g++ and MSVC produce similar run times with optimized code.
> However when moving from g++ 3.2 to 3.4 (and, I think, this also happened
> with 3.3 when I tried it some time ago), the run times increase about
> 2.5x.
> With 3.2 my regressions run in 2 hours (3.0G Pentium D using both cores),
> but run in over 5 hours with 3.4. I can not find anything in particular
> that is
> causing the slowdown.
>
Just a bit more information for anyone that is interested. This appears to
be a Cygwin problem. I tried g++ 3.4 under Linux and it performs nearly
identically to MSVC. Various updates of Cygwin yield a variety of
performance degradations. I'm not sure why.
Peter