static char help[] = "Reads a PETSc matrix and vector from a socket connection,  solves a linear system and sends the result back.\n";

/*T
   Concepts: KSP^solving a linear system
   Processors: n
T*/

/* 
  Include "petscksp.h" so that we can use KSP solvers.  Note that this file
  automatically includes:
     petscsys.h       - base PETSc routines   petscvec.h - vectors
     petscmat.h - matrices
     petscis.h     - index sets            petscksp.h - Krylov subspace methods
     petscviewer.h - viewers               petscpc.h  - preconditioners
*/
#include <petscksp.h>

#undef __FUNCT__
#define __FUNCT__ "main"
int main(int argc,char **args)
{
  KSP            ksp;             /* linear solver context */
  Mat            A;            /* matrix */
  Vec            x,b;          /* approx solution, RHS, exact solution */
  PetscViewer    fd;               /* viewer */
  PetscErrorCode ierr;

  PetscInitialize(&argc,&args,(char *)0,help);
  fd = PETSC_VIEWER_SOCKET_WORLD;

  ierr = VecCreate(PETSC_COMM_WORLD,&b);CHKERRQ(ierr);
  ierr = VecLoad(b,fd);CHKERRQ(ierr);
  ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
  ierr = MatLoad(A,fd);CHKERRQ(ierr);
  ierr = VecDuplicate(b,&x);CHKERRQ(ierr);

  ierr = KSPCreate(PETSC_COMM_WORLD,&ksp);CHKERRQ(ierr);
  ierr = KSPSetOperators(ksp,A,A,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
  ierr = KSPSetFromOptions(ksp);CHKERRQ(ierr);
  ierr = KSPSetUp(ksp);CHKERRQ(ierr);
  ierr = KSPSolve(ksp,b,x);CHKERRQ(ierr);
  ierr = VecView(x,fd);CHKERRQ(ierr);
  ierr = MatDestroy(&A);CHKERRQ(ierr); 
  ierr = VecDestroy(&b);CHKERRQ(ierr);
  ierr = VecDestroy(&x);CHKERRQ(ierr);
  ierr = KSPDestroy(&ksp);CHKERRQ(ierr); 

  ierr = PetscFinalize();
  return 0;
}