Date: 2013-07-02T14:43:59+00:00

Actual source code: ex27.c
petsc-3.4.2 2013-07-02

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

     58:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);

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

     68:   MatDestroy(&C);
     69:   VecDestroy(&x);
     70:   VecDestroy(&y);
     71:   PetscFinalize();
     72:   return 0;
     73: }