[petsc-users] LU Performance

[Dave May]

On Fri, 5 Jul 2019 at 08:19, Jared Crean via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hello,
>
>      I am getting very bad performance from the Umfpack LU solver when I
> use it via Petsc compared to calling Umfpack directly. It takes about
> 5.5 seconds to factor and solve the matrix with Umfpack, but 140 seconds
> when I use Petsc with -ksp_type preonly -pc_type lu
> -pc_factor_mat_solver_type umfpack.
>
>      I have attached a minimal example (test.c) that reads a matrix from
> a file, solves with Umfpack, and then solves with Petsc.  The matrix
> data files are not included because they are about 250 megabytes.  I
> also attached the output of the program with -log_view for
> -pc_factor_mat_solver_type umfpack (fout_umfpacklu) and
> -pc_factor_mat_solver_type petsc (fout_petsclu).  Both results show
> nearly all of the time is spent in MatLuFactorNum.  The times are very
> similar, so I am wondering if Petsc is really calling Umfpack or if the
> Petsc LU solver is getting called in both cases.


Are you using the same umfpack build for both tests (stand alone umfpack
and petsc+umfpack)?

If no, are you certain that the umfpack petsc built links against the same
threaded blas library as the umfpack build which gives the fast result?




>
>
>      Jared Crean
>
>
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