Hi guys, Three questions: 1) As mentioned on the web when we use *-ksp_diagonal_scale_fix: *scale the matrix back AFTER the solve
with -ksp_diagonal_scale does it also scale back the RHS vector associated with the KSP solver? 2) Also, as mentioned on the web for -ksp_diagonal_scale "Tells KSP<http://www.mcs.anl.gov/petsc/petsc-3.1/docs/manualpages/KSP/KSP.html#KSP> to symmetrically diagonally scale the system before solving. " When I used this option to solve for the Pressure (Poisson equation with Neumann B.C., descritized via structured fisytenite-difference method), the number of iterations for convergence was trippled, e.g. without this option, it converges in 18 iteration, but with this option it goes up to 50-60 iterations. (GMRES + BoomerAMG as the preconditioner). Is this something you would expect? 3) How could the linear system resulting from the Poisson equation for pressure (incompressible flow) can be more diagonally scaled? To elaborate more, for the uniform grid case and let's say a second order central scheme finite difference discretization, the sum of the off-diagonal coefficients are equal to the diagonal coefficient. Thanks, Best, Mohamad -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111222/2fc2f101/attachment-0001.htm>
