> If you just want to see the monitor, why not use the command line or > PetscOptionsSetValue()?
I have three ksp's: one for the momentum eqs (GMRES) and one for the pressure eq (CG) inside the SIMPLE preconditioner and one for the matrix-free coupled mass-momentum system (FGMRES). The command line shows me results for all but right now I'm only interested in monitoring FGMRES on the coupled system. > This is the code for setting up the monitor, you can call the part inside > the if statement yourself if you like. > > ierr = PetscOptionsString("-ksp_monitor_singular_value","Monitor > singular > values","KSPMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr); > if (flg) { > ierr = KSPSetComputeSingularValues(ksp,PETSC_TRUE);CHKERRQ(ierr); > ierr = > PetscViewerASCIIOpen(((PetscObject)ksp)->comm,monfilename,&monviewer);CHKERRQ(ierr); > ierr = > KSPMonitorSet(ksp,KSPMonitorSingularValue,monviewer,(PetscErrorCode > (*)(void**))PetscViewerDestroy);CHKERRQ(ierr); > } I'm still confused whether it is supposed to work with FGMRES, the manual states only CG and GMRES. (Besides, I'm using fortran) > How are you applying the action of the linear operator? If you use finite > differencing, it could be inaccurate. Is this incompressible or a low-Mach > compressible formulation? Try -ksp_monitor_true_residual, if the true > residual drifts from the unpreconditioned residual computed by FGMRES, the > Krylov space could be losing orthogonality. You can try > -ksp_gmres_modifiedgramschmidt. Are you losing a lot of progress in > restarts? It's incompressible Navier-Stokes. No finite differencing, the action is computed directly without approximations. It's right preconditioning, so preconditioned and true residual should be the same. I don't get any progress, the residual is stagnating from the very first iteration way before any restart. Regarding modified Gram Schmidt, I tried to set it as follows: call KSPGMRESSetOrthogonalization(ksp,KSPGMRESModifiedGramSchmidtOrthogonalization,ierr) But my compiler tells me: This name does not have a type, and must have an explicit type. [KSPGMRESMODIFIEDGRAMSCHMIDTORTHOGONALIZATIO] (petsc-3.1-p7, fortran with "use petscksp" and #include "finclude/petsckspdef.h") dr. ir. Christiaan Klaij CFD Researcher Research & Development E mailto:C.Klaij at marin.nl T +31 317 49 33 44 MARIN 2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands T +31 317 49 39 11, F +31 317 49 32 45, I www.marin.nl