[Trilinos-Users] Tpetra efficiency

[Einar Otnes]

Thanks,
Well, the test I ran was a first initial test to check the performance on a
single node/thread example. My purpose is to write an application where
dense matrices  will be distributed, and I want to use the functionality of
Thyra  and Tpetra to design compound operators etc.

Thanks,

Einar


On Thu, Jul 21, 2011 at 1:26 PM, Holger Brandsmeier <
holger.brandsmeier at sam.math.ethz.ch> wrote:

> Einer,
>
> VbrMatrix is also a sparse matrix, just a different type of sparse Matrix.
>
> Can't you use Teuchos::SerialDenseMatrix for your needs, in particular
> as you talked about using a single thread. This is what
> Teuchos::SerialDenseMatrix has been developed for. For the Scalar
> types double and complex<double> it uses lapack and blas routines
> which are very efficient for dense matrices.
>
> Unfortunately I do not know about any dense _parallel_ matrix class in
> Trilinos. I don't even know about many dense parallel matrix
> implementations outside of trilinos, in particular not templated as in
> Tpetra / Teuchos. Maybe someone else knows more about this.
>
> -Holger
>
> On Thu, Jul 21, 2011 at 13:47, Einar Otnes <eotnes at gmail.com> wrote:
> > Holger,
> > Thank you for the prompt response. I didn't think about the dense vs
> sparse
> > matrix considerations. Thank you for pointing that out. Do you know
> whether
> > there is a dense matrix class in Tpetra?
> > I was thinking of trying out VbrMatrix using a single block, but I
> haven't
> > been able to make that work, yet. Is that a possible path ?
> >
> > Thanks again,
> > Einar
> >
> > On Thu, Jul 21, 2011 at 12:34 PM, Holger Brandsmeier
> > <holger.brandsmeier at sam.math.ethz.ch> wrote:
> >>
> >> Dear Einar,
> >>
> >> Tpetra::CrsMatrix is a sparse Matrix class, Teuchos::SerialDenseMatrix
> >> is a dense matrix as the name implies. I assume that the matrix you
> >> actually test this with is also dense, then the difference you observe
> >> is certainly to be expected.
> >>
> >> Note that sparse matrices are matrices where many entries are zero.
> >> When there are many zero entries Tpetra::CrsMatrix is fast. But when
> >> all entries are different than zero, then Tpetra::CrsMatrix is slower,
> >> as it has not been desinged for it. The factor of 2 is quite low,
> >> considering that you are using Tpetra::CrsMatrix for something it has
> >> not been designed for.
> >>
> >> -Holger
> >>
> >> On Thu, Jul 21, 2011 at 13:08, Einar Otnes <eotnes at gmail.com> wrote:
> >> > Dear experts,
> >> >
> >> > I have been testing the performance of a simple matrix multiplication
> >> > using
> >> > 2 different Matrix/Vector classes on a single node and using a single
> >> > thread, i.e. Teuchos::SerialDenseMatrix/Vector and Tpetra::CrsMatrix
> and
> >> > Tpetra::Vector, and I have seen that the run time for evaluating the
> >> > same
> >> > product differs by a factor ~2  between the SerialDenseMatrix and
> >> > CrsMatrix.
> >> > Is this  behaviour expected when running on a single node/single
> thread?
> >> > Or
> >> > is the way I'm the Tpetra matrices making my code inefficient? Below
> >> > follows
> >> > the output from my code showing the time it takes to run 200
> evaluations
> >> > of
> >> > Ax=b where the size of the matrix A is 5000x5000.
> >> >
> >> > I have attached the code I wrote to produce the results below.
> >> >
> >> > All the best,
> >> > Einar Otnes
> >> >
> >> >
> >> >
> >> >
> ==========================================================================
> >> >
> >> > Teuchos in Trilinos 10.6.4
> >> > Tpetra in Trilinos 10.6.4
> >> >
> >> > Evaluate Ax=b.
> >> > Problem size: numRows m= 5000 numCols n= 5000
> >> > Ax=b will be evaluated 200 time(s).
> >> > Initialize the Matrices and Vectors with random numbers
> >> > Start the Calculations!!
> >> > Done Ax=b using Teuchos::SerialDenseMatrix
> >> > Done Ax=b using Tpetra::CrsMatrix
> >> > Done Ax=b using Thyra/Tpetra adapter
> >> >
> >> > Calculate norm(b) for each of the three methods applied.
> >> > bNorm= 1671.55
> >> > dNorm= 1671.55
> >> > b2Norm= 1671.55
> >> >
> >> > Tpetra Vector
> >> >  Tpetra::Vector<double, int, int, Kokkos::TPINode>{length=5000}
> >> >  node    0: local length=5000
> >> >
> >> > Thyra wrapped Tpetra Vector
> >> >  Thyra::TpetraVector<double, int, int,
> >> > Kokkos::TPINode>{spmdSpace=Thyra::TpetraVectorSpace<double, int, int,
> >> >
> >> >
> Kokkos::TPINode>{globalDim=5000,localSubDim=5000,localOffset=0,comm=Teuchos::SerialComm<long
> >> > int>}}
> >> >
> >> >
> ================================================================================
> >> >
> >> >                               TimeMonitor Results
> >> >
> >> > Timer Name                      Local time (num calls)
> >> >
> >> >
> --------------------------------------------------------------------------------
> >> > SerialDenseMatrix apply Time    3.69 (200)
> >> > CrsMatrix apply Time            7.53 (200)
> >> > Thyra CrsMatrix apply Time      7.43 (200)
> >> >
> >> >
> ================================================================================
> >> >
> >> >
> >> > _______________________________________________
> >> > Trilinos-Users mailing list
> >> > Trilinos-Users at software.sandia.gov
> >> > http://software.sandia.gov/mailman/listinfo/trilinos-users
> >> >
> >> >
> >>
> >>
> >>
> >> --
> >> Holger Brandsmeier, SAM, ETH Zürich
> >> http://www.sam.math.ethz.ch/people/bholger
> >
> >
>
>
>
> --
> Holger Brandsmeier, SAM, ETH Zürich
> http://www.sam.math.ethz.ch/people/bholger
>
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