typedef struct{

  Mat A;
  Vec VC; /* Work vector in the column space */
  Vec VR; /* Work vector in the row space */
  IS Rows, Cols;

} _p_MatSubMatFreeCtx;

typedef  _p_MatSubMatFreeCtx* MatSubMatFreeCtx;

PetscErrorCode MatCreateSubMatrixFree(Mat,IS,IS,Mat*);
PetscErrorCode MatSMFResetRowColumn(Mat,IS,IS);
PetscErrorCode MatMult_SMF(Mat,Vec,Vec);
PetscErrorCode MatMultTranspose_SMF(Mat,Vec,Vec);
PetscErrorCode MatDiagonalSet_SMF(Mat,Vec,InsertMode);
PetscErrorCode MatDestroy_SMF(Mat);
PetscErrorCode MatView_SMF(Mat,PetscViewer);
PetscErrorCode MatShift_SMF(Mat,PetscReal);
PetscErrorCode MatDuplicate_SMF(Mat,MatDuplicateOption,Mat*);
PetscErrorCode MatEqual_SMF(Mat,Mat,PetscBool*);
PetscErrorCode MatScale_SMF(Mat,PetscReal);
PetscErrorCode MatCreateSubMatrix_SMF(Mat,IS,IS,MatReuse,Mat *);
PetscErrorCode MatCreateSubMatrices_SMF(Mat,PetscInt,IS*,IS*,MatReuse,Mat**);
PetscErrorCode MatTranspose_SMF(Mat,Mat*);
PetscErrorCode MatGetDiagonal_SMF(Mat,Vec);
PetscErrorCode MatGetColumnVector_SMF(Mat,Vec, PetscInt);
PetscErrorCode MatNorm_SMF(Mat,NormType,PetscReal *);
PetscErrorCode MatGetRowMax_SMF(Mat, Vec);
PetscErrorCode MatGetRow_SMF(Mat,PetscInt,PetscInt *,const PetscInt **,const PetscScalar **);
PetscErrorCode MatRestoreRow_SMF(Mat,PetscInt,PetscInt *,const PetscInt **,const PetscScalar **);