On Wed, Feb 22, 2012 at 08:52, Kuhlemann, Verena <vkuhlem@emory.edu> wrote:

I am not sure that I understand the MatStructure flag in the call of KSPSetOperators

correctly.

If I use KSPSetOperators(ksp, A, P, DIFFERENT_NONZERO_PATTERN) and then

solve two linear systems with the same matrix operators but different rhs is

the preconditioner reassembled in every solve. I.e., if I call

KSPSolve(ksp,b1,x1);

KSPSolve(ksp,b2,x2);

If you don't put anything between these calls, the preconditioner will be reused.

And if I use KSPSetOperators(ksp, A, P, SAME_PRECONDITIONER) the preconditioner is

only setup one time and reused later.

Or is the flag only important if I change the matrix operators in between.