Hello, In order to achieve reasonable performance for Helmholtz with PML, Erlangga in his paper used
1) Matrix dependent interpolation in the multigrid. The operators are nonlinear, for example an intermediate computation reads something like d = max(|a+c|, |b|, …) 2) Full weighting (This is linear, so I believe I can achieve that with PCMGSetRestriction). 3) F-cycle with one pre- and postsmoothing with the Jacobi iteration and relaxation factor ω = 0.5. I am not sure how to do 1 & 3 in PETSc. Can anyone suggest a way of implementing these? Thanks, Artur PS. for anyone curious, the paper is "Advances in Iterative Methods and Preconditioners for the Helmholtz Equation"
