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 DM da; 40 Vec local,global,natural; 41 PetscInt i,start,end,*ifrom,x,y,xm,ym; 42 PetscScalar *xnatural; 43 IS from,to; 44 AO ao; 45 VecScatter scatter1,scatter2; 46 PetscViewer subviewer; 47 48 PetscFunctionBeginUser; 49 PetscCall(PetscInitialize(&argc,&argv,(char*)0,help)); 50 51 /* Create distributed array and get vectors */ 52 PetscCall(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 PetscCall(DMSetUp(da)); 54 PetscCall(DMCreateGlobalVector(da,&global)); 55 PetscCall(DMCreateLocalVector(da,&local)); 56 57 /* construct global to local scatter for the left side of the domain to the ghost on the bottom */ 58 PetscCall(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 PetscCall(ISCreateStride(PETSC_COMM_SELF,xm,1,1,&to)); 61 } else { 62 PetscCall(ISCreateStride(PETSC_COMM_SELF,0,0,0,&to)); 63 } 64 PetscCall(PetscMalloc1(xm,&ifrom)); 65 for (i=x;i<x+xm;i++) { 66 ifrom[i-x] = M*i; 67 } 68 PetscCall(DMDAGetAO(da,&ao)); 69 PetscCall(AOApplicationToPetsc(ao,xm,ifrom)); 70 if (!y) { 71 PetscCall(ISCreateGeneral(PETSC_COMM_WORLD,xm,ifrom,PETSC_OWN_POINTER,&from)); 72 } else { 73 PetscCall(PetscFree(ifrom)); 74 PetscCall(ISCreateGeneral(PETSC_COMM_WORLD,0,NULL,PETSC_COPY_VALUES,&from)); 75 } 76 PetscCall(VecScatterCreate(global,from,local,to,&scatter1)); 77 PetscCall(ISDestroy(&to)); 78 PetscCall(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 PetscCall(ISCreateStride(PETSC_COMM_SELF,ym,xm+2,xm+2,&to)); 83 } else { 84 PetscCall(ISCreateStride(PETSC_COMM_SELF,0,0,0,&to)); 85 } 86 PetscCall(PetscMalloc1(ym,&ifrom)); 87 for (i=y;i<y+ym;i++) { 88 ifrom[i-y] = i; 89 } 90 PetscCall(DMDAGetAO(da,&ao)); 91 PetscCall(AOApplicationToPetsc(ao,ym,ifrom)); 92 if (!x) { 93 PetscCall(ISCreateGeneral(PETSC_COMM_WORLD,ym,ifrom,PETSC_OWN_POINTER,&from)); 94 } else { 95 PetscCall(PetscFree(ifrom)); 96 PetscCall(ISCreateGeneral(PETSC_COMM_WORLD,0,NULL,PETSC_COPY_VALUES,&from)); 97 } 98 PetscCall(VecScatterCreate(global,from,local,to,&scatter2)); 99 PetscCall(ISDestroy(&to)); 100 PetscCall(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 PetscCall(DMDACreateNaturalVector(da,&natural)); 107 PetscCall(VecGetOwnershipRange(natural,&start,&end)); 108 PetscCall(VecGetArray(natural,&xnatural)); 109 for (i=start; i<end; i++) { 110 xnatural[i-start] = i; 111 } 112 PetscCall(VecRestoreArray(natural,&xnatural)); 113 PetscCall(DMDANaturalToGlobalBegin(da,natural,INSERT_VALUES,global)); 114 PetscCall(DMDANaturalToGlobalEnd(da,natural,INSERT_VALUES,global)); 115 PetscCall(VecDestroy(&natural)); 116 117 /* scatter from global to local */ 118 PetscCall(VecScatterBegin(scatter1,global,local,INSERT_VALUES,SCATTER_FORWARD)); 119 PetscCall(VecScatterEnd(scatter1,global,local,INSERT_VALUES,SCATTER_FORWARD)); 120 PetscCall(VecScatterBegin(scatter2,global,local,INSERT_VALUES,SCATTER_FORWARD)); 121 PetscCall(VecScatterEnd(scatter2,global,local,INSERT_VALUES,SCATTER_FORWARD)); 122 /* 123 normally here you would also call 124 PetscCall(DMGlobalToLocalBegin(da,global,INSERT_VALUES,local)); 125 PetscCall(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 PetscCall(PetscViewerGetSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&subviewer)); 132 PetscCall(VecView(local,subviewer)); 133 PetscCall(PetscViewerRestoreSubViewer(PETSC_VIEWER_STDOUT_WORLD,PETSC_COMM_SELF,&subviewer)); 134 135 PetscCall(VecScatterDestroy(&scatter1)); 136 PetscCall(VecScatterDestroy(&scatter2)); 137 PetscCall(VecDestroy(&local)); 138 PetscCall(VecDestroy(&global)); 139 PetscCall(DMDestroy(&da)); 140 PetscCall(PetscFinalize()); 141 return 0; 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