:-)
> On Mar 4, 2025, at 5:17 PM, Emmanuel Ayala <juan...@gmail.com> wrote:
>
>
> Well, I just tested the configuration with --download-f2cblaslapack
> --download-blis and the direct solver cholesky with mumps becomes 10x faster
> :D
>
> Thanks!
>
> El mar, 4 mar 2025 a la(s) 3:21 p.m., Emmanuel Ayala (juan...@gmail.com
> <mailto:juan...@gmail.com>) escribió:
>> Thanks for the notes.
>>
>> El mar, 4 mar 2025 a la(s) 2:22 p.m., Barry Smith (bsm...@petsc.dev
>> <mailto:bsm...@petsc.dev>) escribió:
>>>
>>>
>>> > On Mar 4, 2025, at 2:02 PM, Emmanuel Ayala <juan...@gmail.com
>>> > <mailto:juan...@gmail.com>> wrote:
>>> >
>>> > Hello everyone.
>>> >
>>> > I'm trying to solve a linear system (which comes from 3D FEM with
>>> > structured DM mesh) with a direct solver. I configured petsc installation
>>> > with mumps (–download-mumps –download-scalapack –download-parmetis
>>> > –download-metis, --download-hwloc, without ptscotch) and I have the
>>> > following functions:
>>> >
>>> > // K is the stiffness matrix, assembly correctly
>>> > // U is the solution vector
>>> > // RHS is the right hand side of the linear equation
>>> >
>>> > Mat Kfactor;
>>> >
>>> > ierr = MatGetFactor(K,MATSOLVERMUMPS, MAT_FACTOR_CHOLESKY, &Kfactor);
>>> > CHKERRQ(ierr);
>>> > ierr = MatCholeskyFactorSymbolic(Kfactor,K,0,0); CHKERRQ(ierr);
>>> > ierr = MatCholeskyFactorNumeric(Kfactor,K,0); CHKERRQ(ierr);
>>> > ierr = MatSolve(Kfactor,RHS,U);
>>>
>>>
>>> Note 1) these four lines of code above are not needed if you use are using
>>> KSPSolve to solve the system. The options below will trigger this.
>>> >
>>> > and run with options:
>>> > -pc_type cholesky -pc_factor_mat_solver_type mumps -mat_mumps_icntl_1
>>> > 1 -mat_mumps_icntl_13 0 -mat_mumps_icntl_28 2 -mat_mumps_icntl_29 2
>> OK. I'm solving sepparetelly the direct solver and the iterative one.
>>>
>>> Note 2) it is imperative you use a good BLAS library and optimization when
>>> using mumps. Do not use --download-blaslapack (or friends) and use
>>> --with-debugging=0 in the configure option).
>> Right. I configured it with --with-debugging=0 and --download-fblaslapack.
>> So, which is a good BLAS library? from petsc: ...One can use
>> --download-f2cblaslapack --download-blis...
>>>
>>> Note 3) If you are running sequentially (no MPI) then also ensure you have
>>> --with-openmp in your configure options and set an appropriate value for
>>> the number of OpenMP threads when you run your program.
>> I'm running with MPI .
>>
>> Regards.
>>>
>>>
>>> >
>>> > PROBLEM:
>>> > I got the correct solution, but the function MatCholeskyFactorNumeric( )
>>> > takes too much time to be completed. MatCholeskyFactorSymbolic() and
>>> > MatSolve() are very fast. The test uses a square K matrix of 700k dofs,
>>> > and the MatCholeskyFactorNumeric() takes around 14 minutes, while an
>>> > iterative solver (KSPCG/PCJACOBI) takes 5 seconds to get the solution.
>>> > Any suggestions?
>>> >
>>> > Thanks in advance.
>>>
