Actual source code: ex36.c

petsc-3.12.1 2019-10-22
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  1: static char help[] = "Parallel vector layout.\n\n";

  3: /*T
  4:    Concepts: vectors^setting values
  5:    Concepts: vectors^local access to
  6:    Concepts: vectors^drawing vectors;
  7:    Processors: n
  8: T*/

 10: /*
 11:   Include "petscvec.h" so that we can use vectors.  Note that this file
 12:   automatically includes:
 13:      petscsys.h       - base PETSc routines   petscis.h     - index sets
 14:      petscviewer.h - viewers
 15: */
 16:  #include <petscvec.h>

 18: int main(int argc,char **argv)
 19: {
 21:   PetscMPIInt    rank;
 22:   PetscInt       i,istart,iend,n = 6,m,*indices;
 23:   PetscScalar    *values;
 24:   Vec            x;
 25:   PetscBool      set_option_negidx = PETSC_FALSE, set_values_negidx = PETSC_FALSE, get_values_negidx = PETSC_FALSE;

 27:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
 28:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 30:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
 31:   PetscOptionsGetBool(NULL,NULL, "-set_option_negidx", &set_option_negidx, NULL);
 32:   PetscOptionsGetBool(NULL,NULL, "-set_values_negidx", &set_values_negidx, NULL);
 33:   PetscOptionsGetBool(NULL,NULL, "-get_values_negidx", &get_values_negidx, NULL);

 35:   VecCreate(PETSC_COMM_WORLD,&x);
 36:   VecSetSizes(x,PETSC_DECIDE,n);
 37:   VecSetFromOptions(x);

 39:   /* If we want to use negative indices, set the option */
 40:   VecSetOption(x, VEC_IGNORE_NEGATIVE_INDICES,set_option_negidx);

 42:   VecGetOwnershipRange(x,&istart,&iend);
 43:   m    = iend - istart;

 45:   PetscMalloc1(n,&values);
 46:   PetscMalloc1(n,&indices);

 48:   for (i=istart; i<iend; i++) {
 49:     values[i - istart] = (rank + 1) * i * 2;
 50:     if (set_values_negidx) indices[i - istart] = (-1 + 2*(i % 2)) * i;
 51:     else                   indices[i - istart] = i;
 52:   }

 54:   PetscSynchronizedPrintf(PETSC_COMM_WORLD, "%d: Setting values...\n", rank);
 55:   for (i = 0; i<m; i++) {
 56:     PetscSynchronizedPrintf(PETSC_COMM_WORLD,"%d: idx[%D] == %D; val[%D] == %f\n",rank,i,indices[i],i,(double)PetscRealPart(values[i]));
 57:   }
 58:   PetscSynchronizedFlush(PETSC_COMM_WORLD,PETSC_STDOUT);

 60:   VecSetValues(x, m, indices, values, INSERT_VALUES);

 62:   /*
 63:      Assemble vector.
 64:   */

 66:   VecAssemblyBegin(x);
 67:   VecAssemblyEnd(x);

 69:   /*
 70:      Extract values from the vector.
 71:   */

 73:   for (i=0; i<m; i++) {
 74:     values[i] = -1.0;
 75:     if (get_values_negidx) indices[i] = (-1 + 2*((istart+i) % 2)) * (istart+i);
 76:     else                   indices[i] = istart+i;
 77:   }

 79:   PetscSynchronizedPrintf(PETSC_COMM_WORLD, "%d: Fetching these values from vector...\n", rank);
 80:   for (i=0; i<m; i++) {
 81:     PetscSynchronizedPrintf(PETSC_COMM_WORLD, "%d: idx[%D] == %D\n", rank, i, indices[i]);
 82:   }
 83:   PetscSynchronizedFlush(PETSC_COMM_WORLD,PETSC_STDOUT);

 85:   VecGetValues(x, m, indices, values);

 87:   PetscSynchronizedPrintf(PETSC_COMM_WORLD, "%d: Fetched values:\n", rank);
 88:   for (i = 0; i<m; i++) {
 89:     PetscSynchronizedPrintf(PETSC_COMM_WORLD, "%d: idx[%D] == %D; val[%D] == %f\n",rank,i,indices[i],i,(double)PetscRealPart(values[i]));
 90:   }
 91:   PetscSynchronizedFlush(PETSC_COMM_WORLD,PETSC_STDOUT);

 93:   /*
 94:      Free work space.
 95:   */

 97:   VecDestroy(&x);
 98:   PetscFree(values);
 99:   PetscFree(indices);

101:   PetscFinalize();
102:   return ierr;
103: }



107: /*TEST

109:    test:
110:       nsize: 2
111:       args: -set_option_negidx -set_values_negidx -get_values_negidx

113: TEST*/