2: static char help[] = "Saves 4by4 block matrix.\n\n";

  4: #include <petscmat.h>

  8: int main(int argc,char **args)
  9: {
 10:   Mat            A;
 11:   PetscInt       i,j;
 13:   PetscMPIInt    size;
 14:   PetscViewer    fd;
 15:   PetscScalar    values[16],one = 1.0;
 16:   Vec            x;

 18:   PetscInitialize(&argc,&args,(char*)0,help);
 19:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 20:   if (size > 1) SETERRQ(PETSC_COMM_WORLD,1,"Can only run on one processor");

 22:   /*
 23:      Open binary file.  Note that we use FILE_MODE_WRITE to indicate
 24:      writing to this file.
 25:   */
 26:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,"4by4",FILE_MODE_WRITE,&fd);

 28:   MatCreateSeqBAIJ(PETSC_COMM_WORLD,4,12,12,0,0,&A);

 30:   for (i=0; i<16; i++) values[i] = i;
 31:   for (i=0; i<4; i++) values[4*i+i] += 5;
 32:   i    = 0; j = 0;
 33:   MatSetValuesBlocked(A,1,&i,1,&j,values,INSERT_VALUES);

 35:   for (i=0; i<16; i++) values[i] = i;
 36:   i    = 0; j = 2;
 37:   MatSetValuesBlocked(A,1,&i,1,&j,values,INSERT_VALUES);

 39:   for (i=0; i<16; i++) values[i] = i;
 40:   i    = 1; j = 0;
 41:   MatSetValuesBlocked(A,1,&i,1,&j,values,INSERT_VALUES);

 43:   for (i=0; i<16; i++) values[i] = i;for (i=0; i<4; i++) values[4*i+i] += 6;
 44:   i    = 1; j = 1;
 45:   MatSetValuesBlocked(A,1,&i,1,&j,values,INSERT_VALUES);

 47:   for (i=0; i<16; i++) values[i] = i;
 48:   i    = 2; j = 0;
 49:   MatSetValuesBlocked(A,1,&i,1,&j,values,INSERT_VALUES);

 51:   for (i=0; i<16; i++) values[i] = i;for (i=0; i<4; i++) values[4*i+i] += 7;
 52:   i    = 2; j = 2;
 53:   MatSetValuesBlocked(A,1,&i,1,&j,values,INSERT_VALUES);

 55:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 56:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
 57:   MatView(A,fd);
 58:   MatDestroy(&A);

 60:   VecCreateSeq(PETSC_COMM_WORLD,12,&x);
 61:   VecSet(x,one);
 62:   VecView(x,fd);
 63:   VecDestroy(&x);

 65:   PetscViewerDestroy(&fd);
 66:   PetscFinalize();
 67:   return 0;
 68: }