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Hi,<br><br>
maybe I reached my goal; I wanted to be a little polemic to see if,
someone who knows more things about that, can give us a clear answer. I
tested a multicore machine with a commercial software, and I noted that
some speed-up can be obtained (not as good as expected, but much more
than I have)... :)<br><br>
The problem is that I didn't find any clear answer on the
references I was able to find.<br>
I looked on the network to have some suggestions, but I confess that I
didn't find anything really effective. <br>
I tried the options indicated in the OpenMP manual; I'm not a computer
scientist, but a simple user, and using them I was unable to have any
increase in the speed-up.<br><br>
Things where totally different with mpi: in few days, attending a good
school, and also using a very good materials available on the network,,
it has been very easy to see the results of my effort. Maybe this
problems is more difficult; maybe I'm unable to find the good references.
Maybe I don't have the capability. In any case, it seems I'm not the only
one with these problems. <br><br>
Please, if someone have some clear references, share them with the
community (I'm asking references, not the solutions! We are not expecting
something falling from the sky ... in case, we will buy a commercial
software :) ). <br><br>
Gaetano<br><br>
<br>
At 23.06 14/07/2008, you wrote:<br><br>
<br>
<blockquote type=cite class=cite cite="">In defend of the designers of
the multi-core CPUs, I like to say you are wrong in saying so. You
re given a Jet plane, but prefer to use it as a boat, no wonder it
sunk.<br><br>
<br><br>
tan<br><br>
<br>
--- On <b>Mon, 7/14/08, Gaetano Bellanca
<i><gaetano.bellanca@unife.it></i></b> wrote:<br>
<dl>
<dd>From: Gaetano Bellanca <gaetano.bellanca@unife.it><br>
<dd>Subject: Re: [mpich-discuss] Why is my quad core slower than
cluster<br>
<dd>To: mpich-discuss@mcs.anl.gov<br>
<dd>Date: Monday, July 14, 2008, 1:39 PM<br><br>
<dd>Hello Gus and list,<br><br>
<dd>I compiled mpich using gcc, no icc. Maybe this could be a good option
to try to obtain better performance.<br><br>
<dd>Anyway, maybe I'm wrong as I'm only a (very very basic) user, but I
don't think it is a mpich problem. <br>
<dd>Using mpich with n=2, the code speeds up as requested (and I think
that 2 different processors are used, looking at htop report). This does
not happen with n=4, where I still observed a (really small) speed-up.
But with n=6 or n=8, no speed-up is observed!<br><br>
<dd>Again, I tried to compile with parallel and openmp (and to write a
very simple code with do loop similar to my original simulator, but
without mpi calls, communications, etc ...). I didn't have the expected
speed-up also in this case. I'm still investigating .... but ... I really
think that multi core are a commercial gadget .... unless you are a very
specialist in writing a dedicated code able to take advantage of the
specific architecture of the processor. <br><br>
<dd>Hope to be wrong ...<br><br>
<dd>Gaetano<br><br>
<hr>
<dd><tt>Gaetano Bellanca - Department of Engineering - University of
Ferrara <br>
<dd>Via Saragat, 1 - 44100 - Ferrara -
ITALY
<br>
<dd>Voice (VoIP): +39 0532 974809
Fax: +39 0532 974870<br>
<dd><a href="mailto:gaetano.bellanca@unife.it">
mailto:gaetano.bellanca@unife.it</a> <br>
<hr>
</tt>
</dl></blockquote>
<x-sigsep><p></x-sigsep>
<hr>
<tt>Gaetano Bellanca - Department of Engineering - University of
Ferrara <br>
Via Saragat, 1 - 44100 - Ferrara -
ITALY
<br>
Voice (VoIP): +39 0532 974809 Fax:
+39 0532 974870<br>
<a href="mailto:gaetano.bellanca@unife.it" eudora="autourl">
mailto:gaetano.bellanca@unife.it</a> <br>
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