#include "petscksp.h"

#undef __FUNCT__
#define __FUNCT__ "main"

int main(int argc, char* argv[])
{
   PetscErrorCode ierr;

   ierr = PetscInitialize(&argc, &argv, PETSC_NULL, PETSC_NULL);
CHKERRQ(ierr);

   Mat A;
   ierr = MatCreateSeqAIJ(PETSC_COMM_SELF, 3, 3, 1, PETSC_NULL, &A);
CHKERRQ(ierr);
   ierr = MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY);
   ierr = MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY);

   ierr = MatShift(A, 1000); CHKERRQ(ierr);

   Vec x, b;
   ierr = VecCreateSeq(PETSC_COMM_SELF, 3, &x); CHKERRQ(ierr);
   ierr = VecShift(x, -10); CHKERRQ(ierr);

   ierr = VecCreateSeq(PETSC_COMM_SELF, 3, &b); CHKERRQ(ierr);
   ierr = VecShift(b, 200); CHKERRQ(ierr);

   KSP ksp;
   ierr = KSPCreate(PETSC_COMM_SELF, &ksp); CHKERRQ(ierr);
   //ierr = KSPSetFromOptions(ksp); CHKERRQ(ierr);

   printf("x before solve\n");
   ierr = VecView(x, PETSC_VIEWER_STDOUT_SELF); CHKERRQ(ierr);
   printf("b before solve\n");
   ierr = VecView(b, PETSC_VIEWER_STDOUT_SELF); CHKERRQ(ierr);

   ierr = KSPSetOperators(ksp, A, A, SAME_NONZERO_PATTERN); CHKERRQ(ierr);
   ierr = KSPSetFromOptions(ksp); CHKERRQ(ierr);
   
   ierr = KSPSolve(ksp, b, x); CHKERRQ(ierr);

   printf("x after solve\n");
   ierr = VecView(x, PETSC_VIEWER_STDOUT_SELF); CHKERRQ(ierr);
   printf("b after solve\n");
   ierr = VecView(b, PETSC_VIEWER_STDOUT_SELF); CHKERRQ(ierr);

   ierr = VecDestroy(x);
   ierr = VecDestroy(b);
   ierr = MatDestroy(A);
   ierr = KSPDestroy(ksp);

   ierr = PetscFinalize(); CHKERRQ(ierr);
}