[Trilinos-Users] strange performance on simple matrix/vector product

[Heroux, Michael A]

Daniele,

A few questions:

1)  I assume first that you are using Epetra_CrsMatrix and its Multiply method.  Correct?

2) How are you importing the matrix into Epetra?

3) How are you compiling Trilinos?  Depending on how the matrix is imported, the Multiply method is very sensitive to either the C++ or the Fortran compiler optimization flags.

Also, there is a performance optimization guide

http://trilinos.sandia.gov/packages/epetra/EpetraPerformanceGuide.pdf

Mike


On 2/28/08 11:11 AM, "Daniele Bettella" <jagfsdfhf at libero.it> wrote:

Hello, I have a strange performance problem on Epetra, using a simple
multiply.
I have two configurations for testing purposes, the first one is a
personal laptop, single core duo T2300 with 1GB of RAM, the second one
is a dual Xeon quad core E5345 with 16GB of RAM

I take as an example the matrix e30r5000 from matrix market. The matrix
is imported into trilinos and multiplied via Epetra multiply function by
a random vector, i take the time and i get 0.0148 seconds on my laptop
and 0.00227 seconds on the dual Xeon; now, since I'm not the only one
using the Xeon I wrote another test for comparison; this time I multiply
"by hand" storing the matrix in crs, this is what I got:
on my laptop - 0.00168 seconds
on the Xeon - 0.00168 seconds
so basically I have the same time on manual implementation, but trilinos
is sensibly slower on the dual xeon.
I prepared many more matrixes on which I tested the same program; on
many of them the Xeon has better times performing the manual multiply
then the laptop, but Trilinos multiply is always slower...

I understand it's quite hard to tell what the problem might be, but is
there something I'm missing?
I mean, I'm using just one core on each machine, but a core on my laptop
is a 1.6Ghz, wether the Xeon goes at 2.33Ghz... 32 bit vs 64 bit, 2MB vs
8MB of cache... and it generally shows on the product I wrote...
if anyone has any idea I'd be gratefull

thanks in advance and sorry for my english

Daniele

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