Actual source code: ex1.c

petsc-3.4.4 2014-03-13
  2: static char help[] = "Tests VecView() contour plotting for 2d DMDAs.\n\n";

  4: /*
  5:   MATLAB must be installed to configure PETSc to have MATLAB engine.
  6: Unless you have specific important reasons for using the MATLAB engine, we do not
  7: recommend it. If you want to use MATLAB for visualization and maybe a little post processing
  8: then you can use the socket viewer and send the data to MATLAB via that.

 10:   VecView() on DMDA vectors first puts the Vec elements into global natural ordering before printing (or plotting)
 11: them. In 2d 5 by 2 DMDA this means the numbering is

 13:      5  6   7   8   9
 14:      0  1   2   3   4

 16: Now the default split across 2 processors with the DM  is (by rank)

 18:     0  0   0  1   1
 19:     0  0   0  1   1

 21: So the global PETSc ordering is

 23:     3  4  5   8  9
 24:     0  1  2   6  7

 26: Use the options
 27:      -da_grid_x <nx> - number of grid points in x direction, if M < 0
 28:      -da_grid_y <ny> - number of grid points in y direction, if N < 0
 29:      -da_processors_x <MX> number of processors in x directio
 30:      -da_processors_y <MY> number of processors in x direction
 31: */

 33: #include <petscdmda.h>

 37: int main(int argc,char **argv)
 38: {
 39:   PetscMPIInt      rank;
 40:   PetscInt         M = -10,N = -8;
 41:   PetscErrorCode   ierr;
 42:   PetscBool        flg = PETSC_FALSE;
 43:   DM               da;
 44:   PetscViewer      viewer;
 45:   Vec              local,global;
 46:   PetscScalar      value;
 47:   DMDABoundaryType bx    = DMDA_BOUNDARY_NONE,by = DMDA_BOUNDARY_NONE;
 48:   DMDAStencilType  stype = DMDA_STENCIL_BOX;
 49: #if defined(PETSC_HAVE_MATLAB_ENGINE)
 50:   PetscViewer mviewer;
 51: #endif

 53:   PetscInitialize(&argc,&argv,(char*)0,help);
 54:   PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"",300,0,300,300,&viewer);
 55: #if defined(PETSC_HAVE_MATLAB_ENGINE)
 56:   PetscViewerMatlabOpen(PETSC_COMM_WORLD,"tmp.mat",FILE_MODE_WRITE,&mviewer);
 57: #endif

 59:   PetscOptionsGetBool(NULL,"-star_stencil",&flg,NULL);
 60:   if (flg) stype = DMDA_STENCIL_STAR;

 62:   /* Create distributed array and get vectors */
 63:   DMDACreate2d(PETSC_COMM_WORLD,bx,by,stype,M,N,PETSC_DECIDE,PETSC_DECIDE,1,1,NULL,NULL,&da);
 64:   DMCreateGlobalVector(da,&global);
 65:   DMCreateLocalVector(da,&local);

 67:   value = -3.0;
 68:   VecSet(global,value);
 69:   DMGlobalToLocalBegin(da,global,INSERT_VALUES,local);
 70:   DMGlobalToLocalEnd(da,global,INSERT_VALUES,local);

 72:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 73:   value = rank+1;
 74:   VecScale(local,value);
 75:   DMLocalToGlobalBegin(da,local,ADD_VALUES,global);
 76:   DMLocalToGlobalEnd(da,local,ADD_VALUES,global);

 78:   flg  = PETSC_FALSE;
 79:   PetscOptionsGetBool(NULL, "-view_global", &flg,NULL);
 80:   if (flg) { /* view global vector in natural ordering */
 81:     VecView(global,PETSC_VIEWER_STDOUT_WORLD);
 82:   }
 83:   DMView(da,viewer);
 84:   VecView(global,viewer);
 85: #if defined(PETSC_HAVE_MATLAB_ENGINE)
 86:   DMView(da,mviewer);
 87:   VecView(global,mviewer);
 88: #endif

 90:   /* Free memory */
 91: #if defined(PETSC_HAVE_MATLAB_ENGINE)
 92:   PetscViewerDestroy(&mviewer);
 93: #endif
 94:   PetscViewerDestroy(&viewer);
 95:   VecDestroy(&local);
 96:   VecDestroy(&global);
 97:   DMDestroy(&da);
 98:   PetscFinalize();
 99:   return 0;
100: }