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

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

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

 23:   PetscStrcpy(type,MATSAME);
 24:   PetscOptionsGetString(PETSC_NULL,"-mat_type",type,256,PETSC_NULL);

 26:   PetscStrcmp(type,MATMPIDENSE,&flg);
 27:   if (flg) {
 28:     MatCreateMPIDense(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,
 29:            m*n,m*n,PETSC_NULL,&C);
 30:   } else {
 31:     MatCreateMPIAIJ(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,
 32:            m*n,m*n,5,PETSC_NULL,5,PETSC_NULL,&C);
 33:   }

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

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

 62:   MatGetSubMatrix(C,isrow,iscol,PETSC_DECIDE,MAT_REUSE_MATRIX,&A);
 63:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);

 65:   ISDestroy(isrow);
 66:   ISDestroy(iscol);
 67:   MatDestroy(A);
 68:   MatDestroy(C);
 69:   PetscFinalize();
 70:   return 0;
 71: }