On Oct 21, 2011, at 2:48 AM, Klaij, Christiaan wrote: >> 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.
http://www.mcs.anl.gov/petsc/petsc-2/snapshots/petsc-current/docs/manualpages/KSP/KSPSetOptionsPrefix.html Give each ksp a unique prefix: for example -momentum -pressure and -mass-momentum Then use -mass-momentum_ksp_monitor_singular_value at the command line. Barry > > > > >> 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 >
