Actual source code: ex3.c

      1: static char help[] = "Demonstrates creating a blocked index set.\n\n";

      3: #include <petscis.h>
      4: #include <petscviewer.h>

      6: int main(int argc, char **argv)
      7: {
      8:   PetscInt        i, n = 4, inputindices[] = {0, 1, 3, 4}, bs = 3, issize;
      9:   const PetscInt *indices;
     10:   IS              set;
     11:   PetscBool       isblock;

     13:   PetscFunctionBeginUser;
     14:   PetscCall(PetscInitialize(&argc, &argv, NULL, help));

     16:   /*
     17:     Create a block index set. The index set has 4 blocks each of size 3.
     18:     The indices are {0,1,2,3,4,5,9,10,11,12,13,14}
     19:     Note each processor is generating its own index set
     20:     (in this case they are all identical)
     21:   */
     22:   PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, n, inputindices, PETSC_COPY_VALUES, &set));
     23:   PetscCall(ISView(set, PETSC_VIEWER_STDOUT_SELF));

     25:   /*
     26:     Extract indices from set.
     27:   */
     28:   PetscCall(ISGetLocalSize(set, &issize));
     29:   PetscCall(ISGetIndices(set, &indices));
     30:   PetscCall(PetscPrintf(PETSC_COMM_SELF, "Printing indices directly\n"));
     31:   for (i = 0; i < issize; i++) PetscCall(PetscPrintf(PETSC_COMM_SELF, "%" PetscInt_FMT "\n", indices[i]));
     32:   PetscCall(ISRestoreIndices(set, &indices));

     34:   /*
     35:     Extract the block indices. This returns one index per block.
     36:   */
     37:   PetscCall(ISBlockGetIndices(set, &indices));
     38:   PetscCall(PetscPrintf(PETSC_COMM_SELF, "Printing block indices directly\n"));
     39:   for (i = 0; i < n; i++) PetscCall(PetscPrintf(PETSC_COMM_SELF, "%" PetscInt_FMT "\n", indices[i]));
     40:   PetscCall(ISBlockRestoreIndices(set, &indices));

     42:   /*
     43:     Check if this is really a block index set
     44:   */
     45:   PetscCall(PetscObjectTypeCompare((PetscObject)set, ISBLOCK, &isblock));
     46:   PetscCheck(isblock, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Index set is not blocked!");

     48:   /*
     49:     Determine the block size of the index set
     50:   */
     51:   PetscCall(ISGetBlockSize(set, &bs));
     52:   PetscCheck(bs == 3, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Block size is not 3!");

     54:   /*
     55:     Get the number of blocks
     56:   */
     57:   PetscCall(ISBlockGetLocalSize(set, &n));
     58:   PetscCheck(n == 4, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Number of blocks not 4!");

     60:   PetscCall(ISDestroy(&set));
     61:   PetscCall(PetscFinalize());
     62:   return 0;
     63: }

     65: /*TEST

     67:    test:

     69: TEST*/