Dear Matt,
Thank you very much for your reply!
So what you mean is that I can just do the KSPSolve() every iteration
once the MUMPS is set?
That means inside the KSPSolve() the numerical factorization is
performed. If that is the case, it seems that the ksp object is
not changed when the values in the matrix are changed.
Or do I need to call both KSPSetOperators() and KSPSolve()?
On 2018-05-04 14:44, Matthew Knepley wrote:
On Fri, May 4, 2018 at 9:40 AM, Y. Shidi <[email protected]> wrote:
Dear PETSc users,
I am currently using MUMPS to solve linear systems directly.
Generally, we use ICNTL(7) or ICNTL(29) to do the preprocessing
step and then solve the system.
In my code, the values in the matrix is changed in each iteration,
but the structure of the matrix stays the same, which means the
performance can be improved if symbolic factorisation is only
performed once. Hence, it is necessary to split the symbolic
and numeric factorisation. However, I cannot find a specific step
(control parameter) to perform the numeric factorisation.
I have used ICNTL(3) and ICNTL(4) to print the MUMPS information,
it seems that the symbolic and numeric factorisation always perform
together.
If you use KSPSolve instead, it will automatically preserve the
symbolic
factorization.
Thanks,
Matt
So I am wondering if anyone has an idea about it.
Below is how I set up MUMPS solver:
PC pc;
PetscBool flg_mumps, flg_mumps_ch;
flg_mumps = PETSC_FALSE;
flg_mumps_ch = PETSC_FALSE;
PetscOptionsGetBool(NULL, NULL, "-use_mumps_lu", &flg_mumps,
NULL);
PetscOptionsGetBool(NULL, NULL, "-use_mumps_ch", &flg_mumps_ch,
NULL);
if(flg_mumps ||flg_mumps_ch)
{
KSPSetType(_ksp, KSPPREONLY);
PetscInt ival,icntl;
PetscReal val;
KSPGetPC(_ksp, &pc);
/// Set preconditioner type
if(flg_mumps)
{
PCSetType(pc, PCLU);
}
else if(flg_mumps_ch)
{
MatSetOption(A, MAT_SPD, PETSC_TRUE);
PCSetType(pc, PCCHOLESKY);
}
PCFactorSetMatSolverPackage(pc, MATSOLVERMUMPS);
PCFactorSetUpMatSolverPackage(pc);
PCFactorGetMatrix(pc, &_F);
icntl = 7; ival = 0;
MatMumpsSetIcntl( _F, icntl, ival );
MatMumpsSetIcntl(_F, 3, 6);
MatMumpsSetIcntl(_F, 4, 2);
}
KSPSetUp(_ksp);
Kind Regards,
Shidi
--
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which
their experiments lead.
-- Norbert Wiener
https://www.cse.buffalo.edu/~knepley/ [1]
Links:
------
[1] http://www.caam.rice.edu/~mk51/
