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

Daniele Bettella jagfsdfhf at libero.it
Fri Feb 29 07:55:14 MST 2008

Thanks for the answer,
1) yes, you are correct, sorry I didn't state it in my original post
2)this is the code used for importing, it's based on the teuchos tutorial

#ifdef HAVE_MPI
  MPI_Init(&argc, &argv);
  Epetra_MpiComm Comm(MPI_COMM_WORLD);
  Epetra_SerialComm Comm;
  Epetra_Map* readMap;
  Epetra_CrsMatrix* readA;
  Epetra_Vector* readx;
  Epetra_Vector* readb;
  Epetra_Vector* readxexact;
  char* matrix_file;
  int matrix_format;
  if(argc > 1){
    matrix_file = argv[1];
    matrix_file = "tols4000.rua";
  Trilinos_Util_ReadHb2Epetra(matrix_file, Comm, readMap, readA, readx, 
readb, readxexact);
  Epetra_Map map(readMap->NumGlobalElements(), 0, Comm);
  Epetra_CrsMatrix A(Copy, map, 0);

  const Epetra_Map &OriginalMap = readA->RowMatrixRowMap() ;
  assert (OriginalMap.SameAs(*readMap));
  Epetra_Export exporter(OriginalMap, map);
  A.Export(*readA, exporter, Add);

3)this is how I configured Trilinos on my laptop
../configure --disable-default-packages --enable-pytrilinos 
--enable-teuchos --enable-epetra --enable-triutils --enable-aztecoo 
on the Xeon I used basically the same command except for the fact that I 
had to use the -fPic flag for cxx, c and fortran flags.

as for compiling the test itself I just use -O3 (same results with -O2)

I read that guide already, thanks for pointing it out, nothing that 
tells me why the same test runs slower on the xeon than on my laptop... 
at least for what I can understand...

hope that helps, thanks again


Heroux, Michael A ha scritto:
> 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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>     Trilinos-Users at software.sandia.gov
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