1 2 static char help[] = "Solves the 1-dimensional wave equation.\n\n"; 3 4 #include <petscdm.h> 5 #include <petscdmda.h> 6 #include <petscdraw.h> 7 8 int main(int argc, char **argv) { 9 PetscMPIInt rank, size; 10 PetscInt M = 60, time_steps = 100, localsize, j, i, mybase, myend, width, xbase, *localnodes = NULL; 11 DM da; 12 PetscViewer viewer, viewer_private; 13 PetscDraw draw; 14 Vec local, global; 15 PetscScalar *localptr, *globalptr; 16 PetscReal a, h, k; 17 PetscBool flg = PETSC_FALSE; 18 19 PetscFunctionBeginUser; 20 PetscCall(PetscInitialize(&argc, &argv, (char *)0, help)); 21 PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank)); 22 PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size)); 23 24 PetscCall(PetscOptionsGetInt(NULL, NULL, "-M", &M, NULL)); 25 PetscCall(PetscOptionsGetInt(NULL, NULL, "-time", &time_steps, NULL)); 26 /* 27 Test putting two nodes on each processor, exact last processor gets the rest 28 */ 29 PetscCall(PetscOptionsGetBool(NULL, NULL, "-distribute", &flg, NULL)); 30 if (flg) { 31 PetscCall(PetscMalloc1(size, &localnodes)); 32 for (i = 0; i < size - 1; i++) localnodes[i] = 2; 33 localnodes[size - 1] = M - 2 * (size - 1); 34 } 35 36 /* Set up the array */ 37 PetscCall(DMDACreate1d(PETSC_COMM_WORLD, DM_BOUNDARY_PERIODIC, M, 1, 1, localnodes, &da)); 38 PetscCall(DMSetFromOptions(da)); 39 PetscCall(DMSetUp(da)); 40 PetscCall(PetscFree(localnodes)); 41 PetscCall(DMCreateGlobalVector(da, &global)); 42 PetscCall(DMCreateLocalVector(da, &local)); 43 44 /* Set up display to show combined wave graph */ 45 PetscCall(PetscViewerDrawOpen(PETSC_COMM_WORLD, 0, "Entire Solution", 20, 480, 800, 200, &viewer)); 46 PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw)); 47 PetscCall(PetscDrawSetDoubleBuffer(draw)); 48 49 /* determine starting point of each processor */ 50 PetscCall(VecGetOwnershipRange(global, &mybase, &myend)); 51 52 /* set up display to show my portion of the wave */ 53 xbase = (int)((mybase) * ((800.0 - 4.0 * size) / M) + 4.0 * rank); 54 width = (int)((myend - mybase) * 800. / M); 55 PetscCall(PetscViewerDrawOpen(PETSC_COMM_SELF, 0, "Local Portion of Solution", xbase, 200, width, 200, &viewer_private)); 56 PetscCall(PetscViewerDrawGetDraw(viewer_private, 0, &draw)); 57 PetscCall(PetscDrawSetDoubleBuffer(draw)); 58 59 /* Initialize the array */ 60 PetscCall(VecGetLocalSize(local, &localsize)); 61 PetscCall(VecGetArray(global, &globalptr)); 62 63 for (i = 1; i < localsize - 1; i++) { 64 j = (i - 1) + mybase; 65 globalptr[i - 1] = PetscSinReal((PETSC_PI * j * 6) / ((PetscReal)M) + 1.2 * PetscSinReal((PETSC_PI * j * 2) / ((PetscReal)M))) * 2; 66 } 67 68 PetscCall(VecRestoreArray(global, &globalptr)); 69 70 /* Assign Parameters */ 71 a = 1.0; 72 h = 1.0 / M; 73 k = h; 74 75 for (j = 0; j < time_steps; j++) { 76 /* Global to Local */ 77 PetscCall(DMGlobalToLocalBegin(da, global, INSERT_VALUES, local)); 78 PetscCall(DMGlobalToLocalEnd(da, global, INSERT_VALUES, local)); 79 80 /*Extract local array */ 81 PetscCall(VecGetArray(local, &localptr)); 82 PetscCall(VecGetArray(global, &globalptr)); 83 84 /* Update Locally - Make array of new values */ 85 /* Note: I don't do anything for the first and last entry */ 86 for (i = 1; i < localsize - 1; i++) globalptr[i - 1] = .5 * (localptr[i + 1] + localptr[i - 1]) - (k / (2.0 * a * h)) * (localptr[i + 1] - localptr[i - 1]); 87 PetscCall(VecRestoreArray(global, &globalptr)); 88 PetscCall(VecRestoreArray(local, &localptr)); 89 90 /* View my part of Wave */ 91 PetscCall(VecView(global, viewer_private)); 92 93 /* View global Wave */ 94 PetscCall(VecView(global, viewer)); 95 } 96 97 PetscCall(DMDestroy(&da)); 98 PetscCall(PetscViewerDestroy(&viewer)); 99 PetscCall(PetscViewerDestroy(&viewer_private)); 100 PetscCall(VecDestroy(&local)); 101 PetscCall(VecDestroy(&global)); 102 103 PetscCall(PetscFinalize()); 104 return 0; 105 } 106 107 /*TEST 108 109 test: 110 nsize: 3 111 args: -time 50 -nox 112 requires: x 113 114 TEST*/ 115