Actual source code: ex4.c
1: /*$Id: ex4.c,v 1.45 2001/08/07 03:03:43 balay Exp $*/
3: static char help[] = "Demonstrates the use of fast Richardson for SOR. And testsn
4: the MatRelax() routines.nn";
6: #include petscpc.h
8: int main(int argc,char **args)
9: {
10: Mat mat;
11: Vec b,u;
12: PC pc;
13: int ierr,n = 5,i,col[3];
14: PetscScalar value[3],zero = 0.0;
16: PetscInitialize(&argc,&args,(char *)0,help);
18: /* Create vectors */
19: VecCreateSeq(PETSC_COMM_SELF,n,&b);
20: VecCreateSeq(PETSC_COMM_SELF,n,&u);
22: /* Create and assemble matrix */
23: MatCreateSeqDense(PETSC_COMM_SELF,n,n,PETSC_NULL,&mat);
24: value[0] = -1.0; value[1] = 2.0; value[2] = -1.0;
25: for (i=1; i<n-1; i++) {
26: col[0] = i-1; col[1] = i; col[2] = i+1;
27: MatSetValues(mat,1,&i,3,col,value,INSERT_VALUES);
28: }
29: i = n - 1; col[0] = n - 2; col[1] = n - 1;
30: MatSetValues(mat,1,&i,2,col,value,INSERT_VALUES);
31: i = 0; col[0] = 0; col[1] = 1; value[0] = 2.0; value[1] = -1.0;
32: MatSetValues(mat,1,&i,2,col,value,INSERT_VALUES);
33: MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY);
34: MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY);
36: /* Create PC context and set up data structures */
37: PCCreate(PETSC_COMM_WORLD,&pc);
38: PCSetType(pc,PCSOR);
39: PCSetFromOptions(pc);
40: PCSetOperators(pc,mat,mat,DIFFERENT_NONZERO_PATTERN);
41: PCSetVector(pc,u);
42: PCSetUp(pc);
44: value[0] = 1.0;
45: for (i=0; i<n; i++) {
46: VecSet(&zero,u);
47: VecSetValues(u,1,&i,value,INSERT_VALUES);
48: PCApply(pc,u,b);
49: VecView(b,PETSC_VIEWER_STDOUT_SELF);
50: }
52: /* Free data structures */
53: MatDestroy(mat);
54: PCDestroy(pc);
55: VecDestroy(u);
56: VecDestroy(b);
57: PetscFinalize();
58: return 0;
59: }
60: