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Hi <br>
<br>
What is the CLASS you are using ?<br>
<br>
One point is how the OpenMP version leads with memory, in relation to
MPI version <br>
<br>
I have two sugestions<br>
<br>
I will be a good ideia to try to use the Intel compiler and<br>
Why not download and run the multi-zone NAS benchmarks ? <br>
It can give a complete view of the "problem"<br>
<br>
They have :<br>
<blockquote type="cite"> NPB3.2-MZ-SER: a serial version<br>
NPB3.2-MZ-MPI: a hybrid MPI + OpenMP version<br>
NPB3.2-MZ-SMP: a hybrid SMP + OpenMP version<br>
</blockquote>
I run in a very small clusters 4 core 2 duo, using Intel compilers and
it seens <br>
and for the CLASS=C I get this numbers for the MPI version and MPI+
OpenMP<br>
with one (Hibrid(1))and two (Hibrib(2)) threads<br>
<blockquote type="cite"><br>
N. Processors - MPI - Hibrid (1) - Hibrid (2)<br>
1 - 2496.59 - * - 1682.07 <br>
2 - 1085.58 - * - 846.82 <br>
4 - 624.69 - 674.28 - 498.65 <br>
8 - 447.7 - 467.79 - * <br>
<br>
</blockquote>
Unfortunate they dont have a version with only OpenMP I and I dont
know if the results with one MPI process and several threads cam be
usefull.<br>
<br>
Notice that the benchmarks are different LU version from the NPB2.0 <br>
they change the "memory acess" .<br>
<br>
<br>
Renato<br>
<br>
<br>
Douglas Eadline wrote:<br>
<blockquote type="cite"
cite="mid46345.192.168.1.1.1197224363.squirrel@mail.eadline.org">
<pre wrap="">I like answering these types of questions with numbers,
so in my Sept 2007 Linux magazine column (which should
be showing up on the website soon) I did the following.
Downloaded the latest NAS benchmarks written in both
OpenMP and MPI. Ran them both on an 8 core Clovertown
(dual socket) system (multiple times) and reported
the following results:
Test OpenMP MPI
gcc/gfortran 4.2 LAM 7.1.2
------------------------------------
CG 790.6 739.1
EP 166.5 162.8
FT 3535.9 2090.8
IS 51.1 122.5
LU 5620.5 5168.8
MG 1616.0 2046.2
My conclusion, it was a draw of sorts.
The article was basically looking at the
lazy assumption that threads (OpenMP) are
always better than MPI on a SMP machine.
I'm going to re-run the tests using Harpertowns
real soon, maybe try other compilers and MPI
versions. It is easy to do. You can get the code here:
<a class="moz-txt-link-freetext" href="http://www.nas.nasa.gov/Resources/Software/npb.html">http://www.nas.nasa.gov/Resources/Software/npb.html</a>
--
Doug
</pre>
<blockquote type="cite">
<pre wrap="">On this list there is almost unanimous agreement that MPI is the way to go
for parallelism and that combining multi-threading (MT) and
message-passing
(MP) is not even worth it, just sticking to MP is all that is necessary.
However, in real-life most are talking and investing in MT while very few
are interested in MP. I also just read on the blog of Arch Robison " TBB
perhaps gives up a little performance short of optimal so you don't have
to
write message-passing " (here:
<a class="moz-txt-link-freetext" href="http://softwareblogs.intel.com/2007/11/17/supercomputing-07-computer-environment-and-evolution/">http://softwareblogs.intel.com/2007/11/17/supercomputing-07-computer-environment-and-evolution/</a>
)
How come there is almost unanimous agreement in the beowulf-community
while
the rest is almost unanimous convinced of the opposite ? Are we just
tapping
ourselves on the back or is MP not sufficiently dissiminated or ... ?
toon
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</pre>
</blockquote>
<pre wrap=""><!---->
--
Doug
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</pre>
</blockquote>
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