1 static char help[] = " Test VecScatter with x, y on different communicators\n\n"; 2 3 #include <petscvec.h> 4 5 int main(int argc, char **argv) 6 { 7 PetscInt i, n = 5, rstart; 8 PetscScalar *val; 9 const PetscScalar *dat; 10 Vec x, y1, y2; 11 MPI_Comm newcomm; 12 PetscMPIInt nproc, rank; 13 IS ix; 14 VecScatter vscat1, vscat2; 15 16 PetscFunctionBegin; 17 PetscFunctionBeginUser; 18 PetscCall(PetscInitialize(&argc, &argv, (char *)0, help)); 19 PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &nproc)); 20 PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank)); 21 22 PetscCheck(nproc == 2, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "This test must run with exactly two MPI ranks"); 23 24 /* Create MPI vectors x and y, which are on the same comm (i.e., MPI_IDENT) */ 25 PetscCall(VecCreateMPI(PETSC_COMM_WORLD, n, PETSC_DECIDE, &x)); 26 PetscCall(VecDuplicate(x, &y1)); 27 PetscCall(VecGetOwnershipRange(x, &rstart, NULL)); 28 29 /* Set x's value locally. x would be {0., 1., 2., ..., 9.} */ 30 PetscCall(VecGetArray(x, &val)); 31 for (i = 0; i < n; i++) val[i] = rstart + i; 32 PetscCall(VecRestoreArray(x, &val)); 33 34 /* Create index set ix = {0, 1, 2, ..., 9} */ 35 PetscCall(ISCreateStride(PETSC_COMM_WORLD, n, rstart, 1, &ix)); 36 37 /* Create newcomm that reverses processes in x's comm, and then create y2 on it*/ 38 PetscCallMPI(MPI_Comm_split(PETSC_COMM_WORLD, 0 /*color*/, -rank /*key*/, &newcomm)); 39 PetscCall(VecCreateMPI(newcomm, n, PETSC_DECIDE, &y2)); 40 41 /* It looks vscat1/2 are the same, but actually not. y2 is on a different communicator than x */ 42 PetscCall(VecScatterCreate(x, ix, y1, ix, &vscat1)); 43 PetscCall(VecScatterCreate(x, ix, y2, ix, &vscat2)); 44 45 PetscCall(VecScatterBegin(vscat1, x, y1, INSERT_VALUES, SCATTER_FORWARD)); 46 PetscCall(VecScatterBegin(vscat2, x, y2, INSERT_VALUES, SCATTER_FORWARD)); 47 PetscCall(VecScatterEnd(vscat1, x, y1, INSERT_VALUES, SCATTER_FORWARD)); 48 PetscCall(VecScatterEnd(vscat2, x, y2, INSERT_VALUES, SCATTER_FORWARD)); 49 50 /* View on rank 0 of x's comm, which is PETSC_COMM_WORLD */ 51 if (rank == 0) { 52 /* Print the part of x on rank 0, which is 0 1 2 3 4 */ 53 PetscCall(PetscPrintf(PETSC_COMM_SELF, "\nOn rank 0 of PETSC_COMM_WORLD, x = ")); 54 PetscCall(VecGetArrayRead(x, &dat)); 55 for (i = 0; i < n; i++) PetscCall(PetscPrintf(PETSC_COMM_SELF, " %.0g", (double)PetscRealPart(dat[i]))); 56 PetscCall(VecRestoreArrayRead(x, &dat)); 57 58 /* Print the part of y1 on rank 0, which is 0 1 2 3 4 */ 59 PetscCall(PetscPrintf(PETSC_COMM_SELF, "\nOn rank 0 of PETSC_COMM_WORLD, y1 = ")); 60 PetscCall(VecGetArrayRead(y1, &dat)); 61 for (i = 0; i < n; i++) PetscCall(PetscPrintf(PETSC_COMM_SELF, " %.0g", (double)PetscRealPart(dat[i]))); 62 PetscCall(VecRestoreArrayRead(y1, &dat)); 63 64 /* Print the part of y2 on rank 0, which is 5 6 7 8 9 since y2 swapped the processes of PETSC_COMM_WORLD */ 65 PetscCall(PetscPrintf(PETSC_COMM_SELF, "\nOn rank 0 of PETSC_COMM_WORLD, y2 = ")); 66 PetscCall(VecGetArrayRead(y2, &dat)); 67 for (i = 0; i < n; i++) PetscCall(PetscPrintf(PETSC_COMM_SELF, " %.0g", (double)PetscRealPart(dat[i]))); 68 PetscCall(VecRestoreArrayRead(y2, &dat)); 69 PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n")); 70 } 71 72 PetscCall(ISDestroy(&ix)); 73 PetscCall(VecDestroy(&x)); 74 PetscCall(VecDestroy(&y1)); 75 PetscCall(VecDestroy(&y2)); 76 PetscCall(VecScatterDestroy(&vscat1)); 77 PetscCall(VecScatterDestroy(&vscat2)); 78 PetscCallMPI(MPI_Comm_free(&newcomm)); 79 PetscCall(PetscFinalize()); 80 return 0; 81 } 82 83 /*TEST 84 85 test: 86 nsize: 2 87 requires: double 88 TEST*/ 89