Re: [firedrake] Tetrahedral mesh

On 10/12/15 15:06, Angwenyi David wrote:

Dear David,

I was trying to solve the indefinite one.

Ah, OK. A few things: 1. Your operator is indefinite, so a ksp_type of 'cg' won't work (conjugate gradient only works for SPD operators), try using 'minres' instead (which works for symmetric indefinite systems). 2. The indefinite Helmholtz problem is notoriously ill-conditioned, and moreover, very difficult to precondition well. If you're not trying to solve problems that are very large, try using a direct solver: {'pc_type': 'lu', 'ksp_type': 'preonly'} Cheers, Lawrence