Actual source code: ex11.c
petsc-3.12.4 2020-02-04
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      2: static char help[] = "Tests the use of MatZeroRows() for uniprocessor matrices.\n\n";

      4:  #include <petscmat.h>

      6: int main(int argc,char **args)
      7: {
      8:   Mat            C;
      9:   PetscInt       i,j,m = 5,n = 5,Ii,J;
     11:   PetscScalar    v,five = 5.0;
     12:   IS             isrow;
     13:   PetscBool      keepnonzeropattern;

     15:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
     16:   /* create the matrix for the five point stencil, YET AGAIN*/
     17:   MatCreate(PETSC_COMM_SELF,&C);
     18:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
     19:   MatSetFromOptions(C);
     20:   MatSetUp(C);
     21:   for (i=0; i<m; i++) {
     22:     for (j=0; j<n; j++) {
     23:       v = -1.0;  Ii = j + n*i;
     24:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
     25:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
     26:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
     27:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
     28:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
     29:     }
     30:   }
     31:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
     32:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

     34:   ISCreateStride(PETSC_COMM_SELF,(m*n)/2,0,2,&isrow);

     36:   PetscOptionsHasName(NULL,NULL,"-keep_nonzero_pattern",&keepnonzeropattern);
     37:   if (keepnonzeropattern) {
     38:     MatSetOption(C,MAT_KEEP_NONZERO_PATTERN,PETSC_TRUE);
     39:   }

     41:   MatZeroRowsIS(C,isrow,five,0,0);

     43:   MatView(C,PETSC_VIEWER_STDOUT_SELF);

     45:   ISDestroy(&isrow);
     46:   MatDestroy(&C);
     47:   PetscFinalize();
     48:   return ierr;
     49: }

     54: /*TEST

     56:    test:

     58:    test:
     59:       suffix: 2
     60:       args: -mat_type seqbaij -mat_block_size 5

     62:    test:
     63:       suffix: 3
     64:       args: -keep_nonzero_pattern

     66:    test:
     67:       suffix: 4
     68:       args: -keep_nonzero_pattern -mat_type seqbaij -mat_block_size 5

     70: TEST*/