Actual source code: ex35.c


  2: static char help[] = "Tests MatCreateSubMatrices().\n\n";

  4: #include <petscmat.h>

  6: int main(int argc,char **args)
  7: {
  8:   Mat            A,B,*Bsub;
  9:   PetscInt       i,j,m = 6,n = 6,N = 36,Ii,J;
 10:   PetscScalar    v;
 11:   IS             isrow;

 13:   PetscInitialize(&argc,&args,(char*)0,help);
 14:   MatCreateSeqAIJ(PETSC_COMM_WORLD,N,N,5,NULL,&A);
 15:   for (i=0; i<m; i++) {
 16:     for (j=0; j<n; j++) {
 17:       v = -1.0;  Ii = j + n*i;
 18:       if (i>0)   {J = Ii - n; MatSetValues(A,1,&Ii,1,&J,&v,INSERT_VALUES);}
 19:       if (i<m-1) {J = Ii + n; MatSetValues(A,1,&Ii,1,&J,&v,INSERT_VALUES);}
 20:       if (j>0)   {J = Ii - 1; MatSetValues(A,1,&Ii,1,&J,&v,INSERT_VALUES);}
 21:       if (j<n-1) {J = Ii + 1; MatSetValues(A,1,&Ii,1,&J,&v,INSERT_VALUES);}
 22:       v = 4.0; MatSetValues(A,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 23:     }
 24:   }
 25:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 26:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
 27:   MatView(A,PETSC_VIEWER_STDOUT_SELF);

 29:   /* take the first diagonal block */
 30:   ISCreateStride(PETSC_COMM_WORLD,m,0,1,&isrow);
 31:   MatCreateSubMatrices(A,1,&isrow,&isrow,MAT_INITIAL_MATRIX,&Bsub);
 32:   B    = *Bsub;
 33:   ISDestroy(&isrow);
 34:   MatView(B,PETSC_VIEWER_STDOUT_SELF);
 35:   MatDestroySubMatrices(1,&Bsub);

 37:   /* take a strided block */
 38:   ISCreateStride(PETSC_COMM_WORLD,m,0,2,&isrow);
 39:   MatCreateSubMatrices(A,1,&isrow,&isrow,MAT_INITIAL_MATRIX,&Bsub);
 40:   B    = *Bsub;
 41:   ISDestroy(&isrow);
 42:   MatView(B,PETSC_VIEWER_STDOUT_SELF);
 43:   MatDestroySubMatrices(1,&Bsub);

 45:   /* take the last block */
 46:   ISCreateStride(PETSC_COMM_WORLD,m,N-m-1,1,&isrow);
 47:   MatCreateSubMatrices(A,1,&isrow,&isrow,MAT_INITIAL_MATRIX,&Bsub);
 48:   B    = *Bsub;
 49:   ISDestroy(&isrow);
 50:   MatView(B,PETSC_VIEWER_STDOUT_SELF);

 52:   MatDestroySubMatrices(1,&Bsub);
 53:   MatDestroy(&A);

 55:   PetscFinalize();
 56:   return 0;
 57: }

 59: /*TEST

 61:    test:

 63: TEST*/