Actual source code: ex27.c

  2: static char help[] = "Tests repeated use of assembly for matrices.\n\
  3:  does nasty case where matrix must be rebuilt.\n\n";

 5:  #include petscmat.h

  9: int main(int argc,char **args)
 10: {
 11:   Mat            C;
 12:   PetscInt       i,j,m = 5,n = 2,I,J;
 14:   PetscMPIInt    rank,size;
 15:   PetscScalar    v;
 16:   Vec            x,y;

 18:   PetscInitialize(&argc,&args,(char *)0,help);
 19:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 20:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 21:   n = 2*size;

 23:   /* Create the matrix for the five point stencil, YET AGAIN */
 24:   MatCreate(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n,&C);
 25:   MatSetFromOptions(C);
 26:   for (i=0; i<m; i++) {
 27:     for (j=2*rank; j<2*rank+2; j++) {
 28:       v = -1.0;  I = j + n*i;
 29:       if (i>0)   {J = I - n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 30:       if (i<m-1) {J = I + n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 31:       if (j>0)   {J = I - 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 32:       if (j<n-1) {J = I + 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 33:       v = 4.0; MatSetValues(C,1,&I,1,&I,&v,INSERT_VALUES);
 34:     }
 35:   }
 36:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 37:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 38:   for (i=0; i<m; i++) {
 39:     for (j=2*rank; j<2*rank+2; j++) {
 40:       v = 1.0;  I = j + n*i;
 41:       if (i>0)   {J = I - n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 42:       if (i<m-1) {J = I + n; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 43:       if (j>0)   {J = I - 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 44:       if (j<n-1) {J = I + 1; MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);}
 45:       v = -4.0; MatSetValues(C,1,&I,1,&I,&v,INSERT_VALUES);
 46:     }
 47:   }
 48:   /* Introduce new nonzero that requires new construction for 
 49:       matrix-vector product */
 50:   if (rank) {
 51:     I = rank-1; J = m*n-1;
 52:     MatSetValues(C,1,&I,1,&J,&v,INSERT_VALUES);
 53:   }
 54:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 55:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 57:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);

 59:   /* Form a couple of vectors to test matrix-vector product */
 60:   VecCreate(PETSC_COMM_WORLD,&x);
 61:   VecSetSizes(x,PETSC_DECIDE,m*n);
 62:   VecSetFromOptions(x);
 63:   VecDuplicate(x,&y);
 64:   v = 1.0; VecSet(&v,x);
 65:   MatMult(C,x,y);

 67:   MatDestroy(C);
 68:   VecDestroy(x);
 69:   VecDestroy(y);
 70:   PetscFinalize();
 71:   return 0;
 72: }