2: static char help[] = "Tests MatCreateSubmatrix() with entire matrix, modified from ex59.c.";

  4:  #include <petscmat.h>

  6: int main(int argc,char **args)
  7: {
  8:   Mat            C,A;
  9:   PetscInt       i,j,m = 3,n = 2,rstart,rend;
 10:   PetscMPIInt    size,rank;
 12:   PetscScalar    v;
 13:   IS             isrow;
 14:   PetscBool      detect_bug = PETSC_FALSE;

 16:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 17:   PetscOptionsHasName(NULL,NULL,"-detect_bug",&detect_bug);
 18:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 19:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 20:   n    = 2*size;

 22:   MatCreate(PETSC_COMM_WORLD,&C);
 23:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 24:   MatSetFromOptions(C);
 25:   MatSetUp(C);

 27:   /*
 28:         This is JUST to generate a nice test matrix, all processors fill up
 29:     the entire matrix. This is not something one would ever do in practice.
 30:   */
 31:   MatGetOwnershipRange(C,&rstart,&rend);
 32:   for (i=rstart; i<rend; i++) {
 33:     for (j=0; j<m*n; j++) {
 34:       v    = i + j + 1;
 35:       MatSetValues(C,1,&i,1,&j,&v,INSERT_VALUES);
 36:     }
 37:   }
 38:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 39:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 40:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_COMMON);
 41:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);
 42:   PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);

 44:   /*
 45:      Generate a new matrix consisting every row and column of the original matrix
 46:   */
 47:   MatGetOwnershipRange(C,&rstart,&rend);
 48: 
 49:   /* Create parallel IS with the rows we want on THIS processor */
 50:   if (detect_bug && !rank) {
 51:     ISCreateStride(PETSC_COMM_WORLD,1,rstart,1,&isrow);
 52:   } else {
 53:     ISCreateStride(PETSC_COMM_WORLD,rend-rstart,rstart,1,&isrow);
 54:   }
 55:   MatCreateSubMatrix(C,isrow,NULL,MAT_INITIAL_MATRIX,&A);

 57:   /* Change C to test the case MAT_REUSE_MATRIX */
 58:   if (!rank ) {
 59:     i = 0; j = 0; v = 100;
 60:     MatSetValues(C,1,&i,1,&j,&v,INSERT_VALUES);
 61:   }
 62:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 63:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 64: 
 65:   MatCreateSubMatrix(C,isrow,NULL,MAT_REUSE_MATRIX,&A);
 66:   PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_COMMON);
 67:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 68:   PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
 69: 
 70:   ISDestroy(&isrow);
 71:   MatDestroy(&A);
 72:   MatDestroy(&C);
 73:   PetscFinalize();
 74:   return ierr;
 75: }