program main
#include "petsc/finclude/petscksp.h"
  use petscksp

  PetscInt N
  PetscBool draw, flg
  PetscReal rnorm, rtwo
  PetscScalar one, mone
  Mat A
  Vec b, x, r
  KSP ksp
  PC pc
  PetscErrorCode ierr
  character*80 mattype

  N = 100
  draw = .FALSE.
  one = 1.0
  mone = -1.0
  rtwo = 2.0

  PetscCallA(PetscInitialize(ierr))
  PetscCallA(PetscPythonInitialize(PETSC_NULL_CHARACTER, PETSC_NULL_CHARACTER, ierr))

  PetscCallA(PetscOptionsGetInt(PETSC_NULL_OPTIONS, PETSC_NULL_CHARACTER, '-N', N, flg, ierr))
  PetscCallA(PetscOptionsGetBool(PETSC_NULL_OPTIONS, PETSC_NULL_CHARACTER, '-draw', draw, flg, ierr))

  PetscCallA(MatCreate(PETSC_COMM_WORLD, A, ierr))
  PetscCallA(MatSetSizes(A, PETSC_DECIDE, PETSC_DECIDE, N, N, ierr))
  PetscCallA(MatSetType(A, 'python', ierr))
  PetscCallA(MatPythonSetType(A, 'example100.py:Laplace1D', ierr))
  PetscCallA(MatPythonGetType(A, mattype, ierr))
  PetscCheckA(mattype == 'example100.py:Laplace1D', PETSC_COMM_WORLD, PETSC_ERR_PLIB, 'Error')
  PetscCallA(MatSetUp(A, ierr))

  PetscCallA(MatCreateVecs(A, x, b, ierr))
  PetscCallA(VecSet(b, one, ierr))

  PetscCallA(KSPCreate(PETSC_COMM_WORLD, ksp, ierr))
  PetscCallA(KSPSetType(ksp, 'python', ierr))
  PetscCallA(KSPPythonSetType(ksp, 'example100.py:ConjGrad', ierr))

  PetscCallA(KSPGetPC(ksp, pc, ierr))
  PetscCallA(PCSetType(pc, 'python', ierr))
  PetscCallA(PCPythonSetType(pc, 'example100.py:Jacobi', ierr))

  PetscCallA(KSPSetOperators(ksp, A, A, ierr))
  PetscCallA(KSPSetFromOptions(ksp, ierr))
  PetscCallA(KSPSolve(ksp, b, x, ierr))

  PetscCallA(VecDuplicate(b, r, ierr))
  PetscCallA(MatMult(A, x, r, ierr))
  PetscCallA(VecAYPX(r, mone, b, ierr))
  PetscCallA(VecNorm(r, NORM_2, rnorm, ierr))
  print *, 'error norm = ', rnorm

  if (draw) then
    PetscCallA(VecView(x, PETSC_VIEWER_DRAW_WORLD, ierr))
    PetscCallA(PetscSleep(rtwo, ierr))
  end if

  PetscCallA(VecDestroy(x, ierr))
  PetscCallA(VecDestroy(b, ierr))
  PetscCallA(VecDestroy(r, ierr))
  PetscCallA(MatDestroy(A, ierr))
  PetscCallA(KSPDestroy(ksp, ierr))

  PetscCallA(PetscFinalize(ierr))
end

!/*TEST
!
!    test:
!      requires: petsc4py
!      localrunfiles: example100.py
!
!TEST*/
