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Re: openmp

From: skaller
Subject: Re: openmp
Date: Mon, 15 Oct 2007 15:43:30 -0000
User-agent: Pan/0.129 (Benson & Hedges Moscow Gold)

On Sat, 13 Oct 2007 20:30:52 -0700, Paul Pluzhnikov wrote:

> skaller <> writes:
>> So which version of g++ first provides openmp support?
> From
>   OpenMP is now supported for the C, C++ and Fortran compilers.

hum ... well I tried this on my amd64x2 machine. A test case
for LU decomposition, dimension 800:

1 thread: 4.7 seconds
2 threads: 13 seconds

Well then I discovered the stupid program was using 'clock()' function.
Which counts the time for BOTH processors!

So I used the time command .. and the threaded version is STILL slower.

BTW: running Linux rt patched kernel..

John Skaller <skaller at users dot sf dot net>
Try Felix, the successor to C++

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