Actual source code: ex4.c
petsc-3.4.2 2013-07-02

      2: static char help[] = "Demonstrates the use of fast Richardson for SOR. And tests\n\
      3: the MatSOR() routines.\n\n";

      5: #include <petscpc.h>

      9: int main(int argc,char **args)
     10: {
     11:   Mat            mat;
     12:   Vec            b,u;
     13:   PC             pc;
     15:   PetscInt       n = 5,i,col[3];
     16:   PetscScalar    value[3];

     18:   PetscInitialize(&argc,&args,(char*)0,help);

     20:   /* Create vectors */
     21:   VecCreateSeq(PETSC_COMM_SELF,n,&b);
     22:   VecCreateSeq(PETSC_COMM_SELF,n,&u);

     24:   /* Create and assemble matrix */
     25:   MatCreateSeqDense(PETSC_COMM_SELF,n,n,NULL,&mat);
     26:   value[0] = -1.0; value[1] = 2.0; value[2] = -1.0;
     27:   for (i=1; i<n-1; i++) {
     28:     col[0] = i-1; col[1] = i; col[2] = i+1;
     29:     MatSetValues(mat,1,&i,3,col,value,INSERT_VALUES);
     30:   }
     31:   i    = n - 1; col[0] = n - 2; col[1] = n - 1;
     32:   MatSetValues(mat,1,&i,2,col,value,INSERT_VALUES);
     33:   i    = 0; col[0] = 0; col[1] = 1; value[0] = 2.0; value[1] = -1.0;
     34:   MatSetValues(mat,1,&i,2,col,value,INSERT_VALUES);
     35:   MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY);
     36:   MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY);

     38:   /* Create PC context and set up data structures */
     39:   PCCreate(PETSC_COMM_WORLD,&pc);
     40:   PCSetType(pc,PCSOR);
     41:   PCSetFromOptions(pc);
     42:   PCSetOperators(pc,mat,mat,DIFFERENT_NONZERO_PATTERN);
     43:   PCSetUp(pc);

     45:   value[0] = 1.0;
     46:   for (i=0; i<n; i++) {
     47:     VecSet(u,0.0);
     48:     VecSetValues(u,1,&i,value,INSERT_VALUES);
     49:     VecAssemblyBegin(u);
     50:     VecAssemblyEnd(u);
     51:     PCApply(pc,u,b);
     52:     VecView(b,PETSC_VIEWER_STDOUT_SELF);
     53:   }

     55:   /* Free data structures */
     56:   MatDestroy(&mat);
     57:   PCDestroy(&pc);
     58:   VecDestroy(&u);
     59:   VecDestroy(&b);
     60:   PetscFinalize();
     61:   return 0;
     62: }