[petsc-users] Question on MATMFFD_WP

[Pierre Seize]

Hello PETSc team and users,

I have a question regarding MATMFFD_WP : the documentation states that 
1) || U || does not change between linear iterations and 2) in GMRES || 
a || = 1 except at restart.

In src/mat/impls/mffd/wp.c, in MatMFFDCompute_WP, I see that the 
computation of || U || is inside an if statement, which I guess 
corresponds to what is stated in the documentation, but the computation 
of || a || is done every time.

Does this mean that || a || is computed at each GMRES iteration, even 
when we know it's 1 ?

I was checking this to see how you handle the case of right 
preconditioning : then in GMRES it is no longer true than || a || == 1, 
i think.


Thank you in advance for your replies.


Pierre Seize