<table cellspacing='0' cellpadding='0' border='0' ><tr><td valign='top' style='font: inherit;'><P><BR>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.</P>
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<P>tan</P>
<P><BR>--- On <B>Mon, 7/14/08, Gaetano Bellanca <I><gaetano.bellanca@unife.it></I></B> wrote:<BR></P>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(16,16,255) 2px solid">From: Gaetano Bellanca <gaetano.bellanca@unife.it><BR>Subject: Re: [mpich-discuss] Why is my quad core slower than cluster<BR>To: mpich-discuss@mcs.anl.gov<BR>Date: Monday, July 14, 2008, 1:39 PM<BR><BR>
<DIV id=yiv299372545>Hello Gus and list,<BR><BR>I compiled mpich using gcc, no icc. Maybe this could be a good option to try to obtain better performance.<BR><BR>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>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>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>Hope to be wrong ...<BR><BR>Gaetano<BR>
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<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" target=_blank rel=nofollow>mailto:gaetano.bellanca@unife.it</A> <BR>
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