[petsc-dev] moving -xxx_view to XXXSetFromOptions()

[Barry Smith]

    Previously we often checked the options for -xxx_view directly in various solvers and other pieces of code. For example in KSPSolve alone we have

  ierr = PetscOptionsGetViewer(PetscObjectComm((PetscObject)ksp),((PetscObject)ksp)->prefix,"-ksp_view_pre",&viewer,&format,&flg);CHKERRQ(ierr);
  if (flg && !PetscPreLoadingOn) {
    ierr = PetscViewerPushFormat(viewer,format);CHKERRQ(ierr);
    ierr = KSPView(ksp,viewer);CHKERRQ(ierr);
    ierr = PetscViewerPopFormat(viewer);CHKERRQ(ierr);
    ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
  }

  ierr = MatViewFromOptions(mat,((PetscObject)ksp)->prefix,"-ksp_view_mat");CHKERRQ(ierr);
  ierr = MatViewFromOptions(premat,((PetscObject)ksp)->prefix,"-ksp_view_pmat");CHKERRQ(ierr);
  ierr = VecViewFromOptions(ksp->vec_rhs,((PetscObject)ksp)->prefix,"-ksp_view_rhs");CHKERRQ(ierr);

  ierr = PetscOptionsHasName(((PetscObject)ksp)->prefix,"-ksp_view_mat_explicit",&flag2);CHKERRQ(ierr);
  if (flag2) {
    Mat A,B;
    ierr = PCGetOperators(ksp->pc,&A,NULL,NULL);CHKERRQ(ierr);
    ierr = MatComputeExplicitOperator(A,&B);CHKERRQ(ierr);
    ierr = MatViewFromOptions(B,((PetscObject)ksp)->prefix,"-ksp_view_mat_explicit");CHKERRQ(ierr);
    ierr = MatDestroy(&B);CHKERRQ(ierr);
  }
  ierr = PetscOptionsHasName(((PetscObject)ksp)->prefix,"-ksp_view_preconditioned_operator_explicit",&flag2);CHKERRQ(ierr);
  if (flag2) {
    Mat B;
    ierr = KSPComputeExplicitOperator(ksp,&B);CHKERRQ(ierr);
    ierr = MatViewFromOptions(B,((PetscObject)ksp)->prefix,"-ksp_view_preconditioned_operator_explicit");CHKERRQ(ierr);
    ierr = MatDestroy(&B);CHKERRQ(ierr);
  }
  ierr = PetscOptionsGetViewer(PetscObjectComm((PetscObject)ksp),((PetscObject)ksp)->prefix,"-ksp_view",&viewer,&format,&flg);CHKERRQ(ierr);
  if (flg && !PetscPreLoadingOn) {
    ierr = PetscViewerPushFormat(viewer,format);CHKERRQ(ierr);
    ierr = KSPView(ksp,viewer);CHKERRQ(ierr);
    ierr = PetscViewerPopFormat(viewer);CHKERRQ(ierr);
    ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
  }

   I think these actually belong in KSPSetFromOptions(). Note that currently these do not have help messages nor would they go into any GUI option setting system plus the options may be checked many times outside the control of the user. 

The problem is many of them involve creating a viewer object (and format) which must be destroyed later. I propose putting them all in XXXSetFromOptions() and with each one using a PetscObjectCompose() to attach them to the XXX object so that when the XXX object is destroyed these
viewers are suitably destroyed. 

   Does anyone see a better alternative?

    Barry