Hmm, cut and paste the output when it crashes.
Also run with -malloc_debug and see what happens
Barry
> On Oct 29, 2024, at 3:13 PM, Daniel Pino Munoz
> <daniel.pino_mu...@mines-paristech.fr> wrote:
>
> Hi Barry,
>
> Thanks for getting back to me!
>
> I tried replacing KSPSetOperators(ksp, J, J); by SNESSetJacobian(snes,J,J,
> MatMFFDComputeJacobian)
>
> and I get the same result = It works in Debug mode but not in Release. I also
> ran valgrind and it did not catch any memory problem.
>
> Any ideas?
>
> PS : You are right regarding the number of iterations of the non
> preconditioned problem. In the previous version of the code that only used a
> KSP, I already had to set -ksp_gmres_restart 100. But thanks for the heads up.
>
> Best,
>
> Daniel
>
> On 29/10/2024 20:01, Barry Smith wrote:
>> Don't call
>>
>> KSPSetOperators(ksp, J, J);
>>
>>
>> instead call
>>
>> SNESSetJacobian(snes,J,J, MatMFFDComputeJacobian)
>>
>> but I am not sure that would explain the crash.
>>
>> BTW: since you are applying no preconditioner if the matrix is
>> ill-conditioned it may take many iterations or not converge. You can try
>> something like -ksp_gmres_restart 100 or similar value to try to improve
>> convergence (default is 30).
>>
>> Barry
>>
>>
>>
>>
>>> On Oct 29, 2024, at 12:37 PM, Daniel Pino Munoz
>>> <daniel.pino_mu...@mines-paristech.fr> wrote:
>>>
>>> Dear all,
>>>
>>> I have a linear problem that I am currently solving with a KSP matrix-free.
>>>
>>> I would like to move on to a non linear problem, so figure I could start by
>>> solving the same linear problem using SNES. So I am setting the problem as
>>> follows:
>>>
>>> SNESCreate(PETSC_COMM_WORLD, &snes);
>>> MatCreateShell(PETSC_COMM_WORLD, n_dofs, n_dofs, PETSC_DETERMINE,
>>> PETSC_DETERMINE, &ctx, &J);
>>> MatCreateShell(PETSC_COMM_WORLD, n_dofs, n_dofs, PETSC_DETERMINE,
>>> PETSC_DETERMINE, &ctx, &B);
>>> MatShellSetOperation(J, MATOP_MULT, (void (*)(void))(Multiplication));
>>> MatCreateVecs(J, &x_sol, &b);
>>> VecDuplicate(x_sol, &r);
>>> SNESSetFromOptions(snes);
>>> SNESSetFunction(snes, r, &(computeResidual), &ctx);
>>> SNESSetUseMatrixFree(snes, PETSC_FALSE, PETSC_TRUE);
>>> SNESGetLineSearch(snes, &linesearch);
>>> SNESGetKSP(snes, &ksp);
>>> KSPSetOperators(ksp, J, J);
>>> KSPSetInitialGuessNonzero(ksp, PETSC_TRUE);
>>>
>>> I tested it with a small problem (compiled in debug) and it works.
>>>
>>> When I compiled it in Release, it crashes with a segfault. I tried running
>>> the Debug version through valgrind, but even for a small problem, it is too
>>> slow. So I was wondering if you guys could see any rocky mistake on the
>>> lines I used above?
>>>
>>> Otherwise, is there any example that uses a SNES combined with a matrix
>>> free KSP operator?
>>>
>>> Thank you,
>>>
>>> Daniel
>>>
