Actual source code: ex59.c

  1: /*$Id: ex59.c,v 1.20 2001/08/07 03:03:07 balay Exp $*/

  3: static char help[] = "Tests MatGetSubmatrix() in parallel.";

 5:  #include petscmat.h

  7: int main(int argc,char **args)
  8: {
  9:   Mat         C,A;
 10:   int         i,j,m = 3,n = 2,rank,size,ierr,rstart,rend;
 11:   PetscScalar v;
 12:   IS          isrow,iscol;
 13:   PetscTruth  flg;
 14:   char        type[256];

 16:   PetscInitialize(&argc,&args,(char *)0,help);
 17:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 18:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 19:   n = 2*size;

 21:   PetscStrcpy(type,MATSAME);
 22:   PetscOptionsGetString(PETSC_NULL,"-mat_type",type,256,PETSC_NULL);

 24:   PetscStrcmp(type,MATMPIDENSE,&flg);
 25:   if (flg) {
 26:     MatCreateMPIDense(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,
 27:            m*n,m*n,PETSC_NULL,&C);
 28:   } else {
 29:     MatCreateMPIAIJ(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,
 30:            m*n,m*n,5,PETSC_NULL,5,PETSC_NULL,&C);
 31:   }

 33:   /*
 34:         This is JUST to generate a nice test matrix, all processors fill up
 35:     the entire matrix. This is not something one would ever do in practice.
 36:   */
 37:   for (i=0; i<m*n; i++) {
 38:     for (j=0; j<m*n; j++) {
 39:       v = i + j + 1;
 40:       MatSetValues(C,1,&i,1,&j,&v,INSERT_VALUES);
 41:     }
 42:   }
 43:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 44:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 45:   PetscViewerSetFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_COMMON);
 46:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);

 48:   /* 
 49:      Generate a new matrix consisting of every second row and column of
 50:    the original matrix
 51:   */
 52:   MatGetOwnershipRange(C,&rstart,&rend);
 53:   /* list the rows we want on THIS processor */
 54:   ISCreateStride(PETSC_COMM_WORLD,(rend-rstart)/2,rstart,2,&isrow);
 55:   /* list ALL the columns we want */
 56:   ISCreateStride(PETSC_COMM_WORLD,(m*n)/2,0,2,&iscol);
 57:   MatGetSubMatrix(C,isrow,iscol,PETSC_DECIDE,MAT_INITIAL_MATRIX,&A);
 58:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

 60:   MatGetSubMatrix(C,isrow,iscol,PETSC_DECIDE,MAT_REUSE_MATRIX,&A);
 61:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

 63:   ISDestroy(isrow);
 64:   ISDestroy(iscol);
 65:   MatDestroy(A);
 66:   MatDestroy(C);
 67:   PetscFinalize();
 68:   return 0;
 69: }