Actual source code: ex73.c
2: static char help[] = "Reads a PETSc matrix from a file partitions it\n\n";
4: /*T
5: Concepts: partitioning
6: Processors: n
7: T*/
9: /*
10: Include "petscmat.h" so that we can use matrices. Note that this file
11: automatically includes:
12: petsc.h - base PETSc routines petscvec.h - vectors
13: petscsys.h - system routines petscmat.h - matrices
14: petscis.h - index sets
15: petscviewer.h - viewers
16: */
17: #include petscksp.h
21: int main(int argc,char **args)
22: {
23: const MatType mtype = MATMPIAIJ; /* matrix format */
24: Mat A,B; /* matrix */
25: PetscViewer fd; /* viewer */
26: char file[PETSC_MAX_PATH_LEN]; /* input file name */
27: PetscTruth flg;
28: PetscInt ierr,*nlocal;
29: PetscMPIInt rank,size;
30: MatPartitioning part;
31: IS is,isn;
33: PetscInitialize(&argc,&args,(char *)0,help);
34: MPI_Comm_size(PETSC_COMM_WORLD,&size);
35: MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
37: /*
38: Determine file from which we read the matrix
39: */
40: PetscOptionsGetString(PETSC_NULL,"-f",file,PETSC_MAX_PATH_LEN-1,&flg);
42: /*
43: Open binary file. Note that we use PETSC_FILE_RDONLY to indicate
44: reading from this file.
45: */
46: PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,PETSC_FILE_RDONLY,&fd);
48: /*
49: Load the matrix and vector; then destroy the viewer.
50: */
51: MatLoad(fd,mtype,&A);
52: PetscViewerDestroy(fd);
54: MatView(A,PETSC_VIEWER_DRAW_WORLD);
56: /*
57: Partition the graph of the matrix
58: */
59: MatPartitioningCreate(PETSC_COMM_WORLD,&part);
60: MatPartitioningSetAdjacency(part,A);
61: MatPartitioningSetFromOptions(part);
62: /* get new processor owner number of each vertex */
63: MatPartitioningApply(part,&is);
64: /* get new global number of each old global number */
65: ISPartitioningToNumbering(is,&isn);
66: PetscMalloc(size*sizeof(PetscInt),&nlocal);
67: /* get number of new vertices for each processor */
68: ISPartitioningCount(is,nlocal);
69: ISDestroy(is);
71: /* get old global number of each new global number */
72: ISInvertPermutation(isn,nlocal[rank],&is);
73: PetscFree(nlocal);
74: ISDestroy(isn);
75: MatPartitioningDestroy(part);
77: ISSort(is);
78: ISAllGather(is,&isn);
81: MatGetSubMatrix(A,is,isn,PETSC_DECIDE,MAT_INITIAL_MATRIX,&B);
82: ISDestroy(is);
83: ISDestroy(isn);
85: MatView(B,PETSC_VIEWER_DRAW_WORLD);
87: /*
88: Free work space. All PETSc objects should be destroyed when they
89: are no longer needed.
90: */
91: MatDestroy(A);
92: MatDestroy(B);
95: PetscFinalize();
96: return 0;
97: }