1 2 static char help[] = "\n\n"; 3 4 /* 5 Demonstrates using DM_BOUNDARY_GHOSTED how to handle a rotated boundary conditions where one edge 6 is connected to its immediate neighbor 7 8 Consider the domain (with natural numbering) 9 10 6 7 8 11 3 4 5 12 0 1 2 13 14 The ghost points along the bottom (directly below the three columns above) should be 0 3 and 6 15 while the ghost points along the left side should be 0 1 2 16 17 Note that the ghosted local vectors extend in both the x and y directions so, for example if we have a 18 single MPI process the ghosted vector has (in the original natural numbering) 19 20 x x x x x 21 2 6 7 8 x 22 1 3 4 5 x 23 0 0 1 2 x 24 x 0 3 6 x 25 26 where x indicates a location that is not updated by the communication and should be used. 27 28 For this to make sense the number of grid points in the x and y directions must be the same 29 30 This ghost point mapping was suggested by: Wenbo Zhao <zhaowenbo.npic@gmail.com> 31 */ 32 33 #include <petscdm.h> 34 #include <petscdmda.h> 35 36 int main(int argc,char **argv) 37 { 38 PetscInt M = 6; 39 PetscErrorCode ierr; 40 DM da; 41 Vec local,global,natural; 42 PetscInt i,start,end,*ifrom,x,y,xm,ym; 43 PetscScalar *xnatural; 44 IS from,to; 45 AO ao; 46 VecScatter scatter1,scatter2; 47 PetscViewer subviewer; 48 49 ierr = PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr; 50 51 /* Create distributed array and get vectors */ 52 CHKERRQ(DMDACreate2d(PETSC_COMM_WORLD,DM_BOUNDARY_GHOSTED,DM_BOUNDARY_GHOSTED,DMDA_STENCIL_STAR,M,M,PETSC_DECIDE,PETSC_DECIDE,1,1,NULL,NULL,&da)); 53 CHKERRQ(DMSetUp(da)); 54 CHKERRQ(DMCreateGlobalVector(da,&global)); 55 CHKERRQ(DMCreateLocalVector(da,&local)); 56 57 /* construct global to local scatter for the left side of the domain to the ghost on the bottom */ 58 CHKERRQ(DMDAGetCorners(da,&x,&y,NULL,&xm,&ym,NULL)); 59 if (!y) { /* only processes on the bottom of the domain fill up the ghost locations */ 60 CHKERRQ(ISCreateStride(PETSC_COMM_SELF,xm,1,1,&to)); 61 } else { 62 CHKERRQ(ISCreateStride(PETSC_COMM_SELF,0,0,0,&to)); 63 } 64 CHKERRQ(PetscMalloc1(xm,&ifrom)); 65 for (i=x;i<x+xm;i++) { 66 ifrom[i-x] = M*i; 67 } 68 CHKERRQ(DMDAGetAO(da,&ao)); 69 CHKERRQ(AOApplicationToPetsc(ao,xm,ifrom)); 70 if (!y) { 71 CHKERRQ(ISCreateGeneral(PETSC_COMM_WORLD,xm,ifrom,PETSC_OWN_POINTER,&from)); 72 } else { 73 CHKERRQ(PetscFree(ifrom)); 74 CHKERRQ(ISCreateGeneral(PETSC_COMM_WORLD,0,NULL,PETSC_COPY_VALUES,&from)); 75 } 76 CHKERRQ(VecScatterCreate(global,from,local,to,&scatter1)); 77 CHKERRQ(ISDestroy(&to)); 78 CHKERRQ(ISDestroy(&from)); 79 80 /* construct global to local scatter for the bottom side of the domain to the ghost on the right */ 81 if (!x) { /* only processes on the left side of the domain fill up the ghost locations */ 82 CHKERRQ(ISCreateStride(PETSC_COMM_SELF,ym,xm+2,xm+2,&to)); 83 } else { 84 CHKERRQ(ISCreateStride(PETSC_COMM_SELF,0,0,0,&to)); 85 } 86 CHKERRQ(PetscMalloc1(ym,&ifrom)); 87 for (i=y;i<y+ym;i++) { 88 ifrom[i-y] = i; 89 } 90 CHKERRQ(DMDAGetAO(da,&ao)); 91 CHKERRQ(AOApplicationToPetsc(ao,ym,ifrom)); 92 if (!x) { 93 CHKERRQ(ISCreateGeneral(PETSC_COMM_WORLD,ym,ifrom,PETSC_OWN_POINTER,&from)); 94 } else { 95 CHKERRQ(PetscFree(ifrom)); 96 CHKERRQ(ISCreateGeneral(PETSC_COMM_WORLD,0,NULL,PETSC_COPY_VALUES,&from)); 97 } 98 CHKERRQ(VecScatterCreate(global,from,local,to,&scatter2)); 99 CHKERRQ(ISDestroy(&to)); 100 CHKERRQ(ISDestroy(&from)); 101 102 /* 103 fill the global vector with the natural global numbering for each local entry 104 this is only done for testing purposes since it is easy to see if the scatter worked correctly 105 */ 106 CHKERRQ(DMDACreateNaturalVector(da,&natural)); 107 CHKERRQ(VecGetOwnershipRange(natural,&start,&end)); 108 CHKERRQ(VecGetArray(natural,&xnatural)); 109 for (i=start; i<end; i++) { 110 xnatural[i-start] = i; 111 } 112 CHKERRQ(VecRestoreArray(natural,&xnatural)); 113 CHKERRQ(DMDANaturalToGlobalBegin(da,natural,INSERT_VALUES,global)); 114 CHKERRQ(DMDANaturalToGlobalEnd(da,natural,INSERT_VALUES,global)); 115 CHKERRQ(VecDestroy(&natural)); 116 117 /* scatter from global to local */ 118 CHKERRQ(VecScatterBegin(scatter1,global,local,INSERT_VALUES,SCATTER_FORWARD)); 119 CHKERRQ(VecScatterEnd(scatter1,global,local,INSERT_VALUES,SCATTER_FORWARD)); 120 CHKERRQ(VecScatterBegin(scatter2,global,local,INSERT_VALUES,SCATTER_FORWARD)); 121 CHKERRQ(VecScatterEnd(scatter2,global,local,INSERT_VALUES,SCATTER_FORWARD)); 122 /* 123 normally here you would also call 124 CHKERRQ(DMGlobalToLocalBegin(da,global,INSERT_VALUES,local)); 125 CHKERRQ(DMGlobalToLocalEnd(da,global,INSERT_VALUES,local)); 126 to update all the interior ghost cells between neighboring processes. 127 We don't do it here since this is only a test of "special" ghost points. 128 */ 129 130 /* view each local ghosted vector */ 131 CHKERRQ(PetscViewerGetSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&subviewer)); 132 CHKERRQ(VecView(local,subviewer)); 133 CHKERRQ(PetscViewerRestoreSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&subviewer)); 134 135 CHKERRQ(VecScatterDestroy(&scatter1)); 136 CHKERRQ(VecScatterDestroy(&scatter2)); 137 CHKERRQ(VecDestroy(&local)); 138 CHKERRQ(VecDestroy(&global)); 139 CHKERRQ(DMDestroy(&da)); 140 ierr = PetscFinalize(); 141 return ierr; 142 } 143 144 /*TEST 145 146 test: 147 148 test: 149 suffix: 2 150 nsize: 2 151 152 test: 153 suffix: 4 154 nsize: 4 155 156 test: 157 suffix: 9 158 nsize: 9 159 160 TEST*/ 161