[petsc-users] User-defined residual norm calculation in PETSC solvers

[Kirill Voronin]

Hello!

Thanks Matthew Knepley and Barry Smith for the answers to my previous
questions!

I am solving Ax = b with PETSC BiCGStab with user-defined preconditioner
and want to compare it with other iteration process.

The question is
1)
Is there a possibility to monitor a user-defined function of residual
norm(e.g., useer-defined computation of NORM_1) at each iteration of PETSC
solver? (I cannot rewrite the user-defined routine for residual norm using
PETSC interface since it is just fixed and given to me)?

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It seems now that the residual norm (L1 = NORM_1) is calculated somewhat
different through PETSC and user-defined routine. The difference is rather
small but still for comparison with other solver I would prefer to have
the same numbers.
As a result, by now I have different values of residual norms measured for
the same data by PETSC and external user-defined routine. (I checked it
just be getting arrays from PETSC vectors and then giving them to the
user-defined routine of residual norm).

I found KSPSetConvergenceTest but the convergence is measured always in
terms of NORM_2 of the error as far as I understand.
Thanks in advance!

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Best regards,

Kirill Voronin