static char help[] = "";

#include <petscksp.h>
#include <petscviewer.h>

#undef __FUNCT__
#define __FUNCT__ "main"
int main(int argc,char **args)
{
    Vec            x,b;
    Mat            A,;
    KSP            ksp;
    PC             pc;
    PetscRandom    rctx;
    PetscInt       M,N;
    PetscErrorCode ierr;
    PetscViewer    viewer;
    PetscReal      maxx,minx;

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

    ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,"A.dat",FILE_MODE_READ,&viewer);CHKERRQ(ierr);
    ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
    ierr = MatSetFromOptions(A);CHKERRQ(ierr);
    ierr = MatLoad(A,viewer);CHKERRQ(ierr);
    ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);

    MatGetSize(A,&N,&M);
    VecCreateMPI(MPI_COMM_WORLD,PETSC_DECIDE,N,&x);
    VecCreateMPI(MPI_COMM_WORLD,PETSC_DECIDE,M,&b);

    KSPCreate(MPI_COMM_WORLD,&ksp);
    KSPSetType(ksp,KSPGMRES);
    KSPSetTolerances(ksp,1.0e-8,PETSC_DEFAULT,PETSC_DEFAULT,100);
    KSPGMRESSetRestart(ksp, 100);
    KSPSetComputeSingularValues(ksp,PETSC_TRUE);
    KSPSetFromOptions(ksp);

    PetscRandomCreate(PETSC_COMM_WORLD,&rctx);
    PetscRandomSetFromOptions(rctx);
    VecSetRandom(b,rctx);

    KSPGetPC(ksp,&pc);
    PCSetType(pc,PCNONE);
    KSPSetOperators(ksp,A,A,SAME_PRECONDITIONER);
    KSPSolve(ksp,b,x);
    KSPComputeExtremeSingularValues(ksp, &maxx, &minx);

    ierr = PetscPrintf(PETSC_COMM_WORLD,"%e \n", maxx);

    KSPDestroy(&ksp);

    MatDestroy(&A);
    VecDestroy(&x);
    VecDestroy(&b);

    ierr = PetscFinalize();

    return 0;
}