Re: [petsc-users] Inverse of a Large Sparse Matrix

On Wed, Jul 26, 2023 at 8:13 AM maitri ksh wrote: > I have a large sparse matrix (48x48) and I need to take its > inverse and use it to solve an eigenvalue problem. According to > petsc-archive > , >

[petsc-users] Inverse of a Large Sparse Matrix

I have a large sparse matrix (48x48) and I need to take its inverse and use it to solve an eigenvalue problem. According to petsc-archive , Barry suggested using superLU with MatMatSolve() (& not

Re: [petsc-users] [petsc-maint] Monolithic AMG with fieldsplit as smoother

On Thu, Jul 27, 2023 at 12:48 AM Jed Brown wrote: > AMG is subtle here. With AMG for systems, you typically feed it elements > of the near null space. In the case of (smoothed) aggregation, the coarse > space will have a regular block structure with block sizes equal to the > number of near-null

Re: [petsc-users] [petsc-maint] Monolithic AMG with fieldsplit as smoother

AMG is subtle here. With AMG for systems, you typically feed it elements of the near null space. In the case of (smoothed) aggregation, the coarse space will have a regular block structure with block sizes equal to the number of near-null vectors. You can use pc_fieldsplit options to select

[petsc-users] Monolithic AMG with fieldsplit as smoother

Hello PETSc team: I wonder if the current PETSc implementation supports using AMG monolithically for a multi-field problem and using fieldsplit in the smoother. Thank you very much, Mike

Re: [petsc-users] [petsc-maint] Monolithic AMG with fieldsplit as smoother

See the very end of the section https://petsc.org/release/manual/ksp/#multigrid-preconditioners on how to control the smoothers (and coarse grid solve) for multigrid in PETSc including for algebraic multigrid. So, for example, -mg_levels_pc_type fieldsplit would be the starting point.