[petsc-users] 2D Poisson on nonuniform meshes

[Filippo Leonardi]

Dear PETSc Users,

I want to use multigrid to solve uniform (just Laplace) poisson in 2D/3D on cartesian, non-
uniform meshes with a standard 5 (7)-points stencil FD.

I always scaled my Poisson matrix like in the doc examples, i.e. multiplying by dx*dy (so that in 
ComputeRHS I need to scale b, in A*x = b, as well). This always worked properly with both MG/
GAMG and with galerkin matrices.

Now I'd like to use non-uniform meshes, therefore the scaling is non-uniform. However I cannot 
get my matrices to scale properly with any sort of multigrid.

One would think that without scaling, i.e. solving the original system, at least MG+galerkin or 
GAMG should work anyways provided the matrix A and b are consistent.

I tried without boundaries (i.e. torus), so this is not the problem.

Anyone did/knows how to do this properly?

Thanks,
F
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