Re: [petsc-users] MatCompositeMerge + MatCreateRedundantMatrix

I have another question regarding MatCreateRedundantMatrix and MPICreateSubMatricesMPI. The former works for MPIAIJ and  MPIDENSE and the later only for MPIAIJ. Would it be possible to use MatCreateRedundantMatrix with a factored matrix and MPICreateSubMatricesMPI with dense and/or elemental

Re: [petsc-users] Confusing Schur preconditioner behaviour

Colin, 1) What equations are you solving? 2) In your second case, you set the outer ksp to preonly, thus we are unable to see the ksp_monitor for the (firedrake_0_) solver. Set it to gmres and see if you have a similar output to your first case: 0 KSP preconditioned resid norm

[petsc-users] Confusing Schur preconditioner behaviour

Dear petsc-users, I'm solving a 2x2 block system, for which I can construct the Schur complement analytically (through compatible FEM stuff), which I can pass as the preconditioning matrix. When using gmres on the outer iteration, and preonly+lu on the inner iterations with a Schur

Re: [petsc-users] BJACOBI with FIELDSPLIT

On Mon, Mar 18, 2019 at 3:56 PM Rossi, Simone via petsc-users < petsc-users@mcs.anl.gov> wrote: > To follow up on that: when would you want to use gmres instead of fgmres > in the outer ksp? > The difference here is just that FGMRES is right-preconditioned by default, so you do not get the extra

Re: [petsc-users] BJACOBI with FIELDSPLIT

On Mon, Mar 18, 2019 at 3:18 PM Rossi, Simone via petsc-users < petsc-users@mcs.anl.gov> wrote: > Dear all, > > I'm debugging my application in which I'm trying to use the FIELDSPLIT > preconditioner for solving a 2x2 block matrix. > > > Currently I'm testing the preconditioner on a decoupled

Re: [petsc-users] BJACOBI with FIELDSPLIT

To follow up on that: when would you want to use gmres instead of fgmres in the outer ksp? Thanks again for the help, Simone From: Rossi, Simone Sent: Monday, March 18, 2019 3:43:04 PM To: Justin Chang Cc: Smith, Barry F.; petsc-users@mcs.anl.gov Subject: Re:

Re: [petsc-users] BJACOBI with FIELDSPLIT

Thanks, using fgmres it does work as expected. I thought gmres would do the same since I'm solving the subblocks "exactly". Simone From: Justin Chang Sent: Monday, March 18, 2019 3:38:34 PM To: Rossi, Simone Cc: Smith, Barry F.; petsc-users@mcs.anl.gov

Re: [petsc-users] BJACOBI with FIELDSPLIT

Use -ksp_type fgmres if your inner ksp solvers are gmres. Maybe that will help? On Mon, Mar 18, 2019 at 1:33 PM Rossi, Simone via petsc-users < petsc-users@mcs.anl.gov> wrote: > Thanks Barry. > > Let me know if you can spot anything out of the ksp_view > > > KSP Object: 1 MPI processes > >

Re: [petsc-users] BJACOBI with FIELDSPLIT

Thanks Barry. Let me know if you can spot anything out of the ksp_view KSP Object: 1 MPI processes type: gmres restart=30, using Classical (unmodified) Gram-Schmidt Orthogonalization with no iterative refinement happy breakdown tolerance 1e-30 maximum iterations=5000, nonzero

Re: [petsc-users] BJACOBI with FIELDSPLIT

Simone, This is indeed surprising, given the block structure of the matrix and the exact block solves we'd expect the solver to converge after the application of the preconditioner. Please send the output of -ksp_view Barry Also if you are willing to share your test code we can try

[petsc-users] BJACOBI with FIELDSPLIT

Dear all, I'm debugging my application in which I'm trying to use the FIELDSPLIT preconditioner for solving a 2x2 block matrix. Currently I'm testing the preconditioner on a decoupled system where I solve two identical and independent Poisson problems. Using the default fieldsplit type