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

[Daniele Bettella]

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