[petsc-users] KSPSetDiagonalScale

[Colin McAuliffe]

Hello!

I am solving a coupled multiphysics problem which has several  
different units, which leads to a poorly conditioned jacobian. I am  
using the following ksp options:

-ksp_type preonly -pc_type lu -pc_factor_mat_solver_package umfpack

The results I am getting are not right and I suspect that the  
conditioning of the jacobian may be playing a part in that. I would  
like to improve the conditioning by using -ksp_diagonal_scale, but  
adding it does not seem to help. The documentation for this option  
says 'this routine is only used if the matrix and preconditioner  
matrix are the same thing'.

Does that mean the command can only be used with no preconditioner?

http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPSetDiagonalScale.html

All the best,

-- 
Colin McAuliffe
PhD Candidate
Columbia University
Department of Civil Engineering and Engineering Mechanics