[petsc-users] Slow linear solver via MUMPS

[Mohammad Gohardoust]

Hi,

I am trying to modify a "pure MPI" code for solving water movement equation
in soils which employs KSP iterative solvers. This code gets really slow in
the hpc I am testing it as I increase the number of calculating nodes (each
node has 28 cores) even from 1 to 2. I went for implementing "MPI-OpenMP"
solutions like MUMPS. I did this inside the petsc by:

KSPSetType(ksp, KSPPREONLY);
PCSetType(pc, PCLU);
PCFactorSetMatSolverType(pc, MATSOLVERMUMPS);
KSPSolve(ksp, ...

and I run it through:

export OMP_NUM_THREADS=16 && mpirun -n 2 ~/Programs/my_programs

The code is working (in my own PC) but it is too slow (maybe about 50 times
slower). Since I am not an expert, I like to know is this what I should
expect from MUMPS!?

Thanks,
Mohammad
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