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: }