[petsc-users] KSP solver iteration stop criteria

[Danyang Su]

Hi All,

Can I control KSP solver iteration by user defined criteria? I would 
like to check both preconditioned residual norm and true residual norm 
in every iteration, and force the solver to stop iteration if either 
criteria matches.

If using KSPSetConvergenceTest, can I get the true residual norm 
directly from a function or shall I compute it in the user-defined 
convergence function:

      call KSPBuildSolution(ksp,PETSC_NULL_OBJECT,x,ierr)
      call KSPGetRhs(ksp, b, ierr)
      call KSPGetOperators(ksp,a,PETSC_NULL_OBJECT ,PETSC_NULL_OBJECT, 
ierr)
      call MatMult(a, x, u, ierr)
      call VecAXPY(u, -1.0d0, b, ierr)
      call VecNormBegin(u, Norm_2, rnorm_true, ierr)
      call VecNormEnd(u, Norm_2, rnorm_true, ierr)

Thanks and regards,

Danyang