Actual source code: ex16.c
2: static char help[] = "Reads a matrix from PETSc binary file. Use for view or investigating matrix data structure. \n\n";
3: /*
4: Example:
5: ./ex16 -f <matrix file> -a_mat_view draw -draw_pause -1
6: ./ex16 -f <matrix file> -a_mat_view ascii::ascii_info
7: */
9: #include <petscmat.h>
10: int main(int argc, char **args)
11: {
12: Mat A, Asp;
13: PetscViewer fd; /* viewer */
14: char file[PETSC_MAX_PATH_LEN]; /* input file name */
15: PetscInt m, n, rstart, rend;
16: PetscBool flg;
17: PetscInt row, ncols, j, nrows, nnzA = 0, nnzAsp = 0;
18: const PetscInt *cols;
19: const PetscScalar *vals;
20: PetscReal norm, percent, val, dtol = 1.e-16;
21: PetscMPIInt rank;
22: MatInfo matinfo;
23: PetscInt Dnnz, Onnz;
25: PetscFunctionBeginUser;
26: PetscCall(PetscInitialize(&argc, &args, (char *)0, help));
27: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
29: /* Determine files from which we read the linear systems. */
30: PetscCall(PetscOptionsGetString(NULL, NULL, "-f", file, sizeof(file), &flg));
31: PetscCheck(flg, PETSC_COMM_WORLD, PETSC_ERR_USER, "Must indicate binary file with the -f option");
33: /* Open binary file. Note that we use FILE_MODE_READ to indicate
34: reading from this file. */
35: PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, file, FILE_MODE_READ, &fd));
37: /* Load the matrix; then destroy the viewer. */
38: PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
39: PetscCall(MatSetOptionsPrefix(A, "a_"));
40: PetscCall(MatSetFromOptions(A));
41: PetscCall(MatLoad(A, fd));
42: PetscCall(PetscViewerDestroy(&fd));
43: PetscCall(MatGetSize(A, &m, &n));
44: PetscCall(MatGetInfo(A, MAT_LOCAL, &matinfo));
45: /*printf("matinfo.nz_used %g\n",matinfo.nz_used);*/
47: /* Get a sparse matrix Asp by dumping zero entries of A */
48: PetscCall(MatCreate(PETSC_COMM_WORLD, &Asp));
49: PetscCall(MatSetSizes(Asp, m, n, PETSC_DECIDE, PETSC_DECIDE));
50: PetscCall(MatSetOptionsPrefix(Asp, "asp_"));
51: PetscCall(MatSetFromOptions(Asp));
52: Dnnz = (PetscInt)matinfo.nz_used / m + 1;
53: Onnz = Dnnz / 2;
54: printf("Dnnz %d %d\n", Dnnz, Onnz);
55: PetscCall(MatSeqAIJSetPreallocation(Asp, Dnnz, NULL));
56: PetscCall(MatMPIAIJSetPreallocation(Asp, Dnnz, NULL, Onnz, NULL));
57: /* The allocation above is approximate so we must set this option to be permissive.
58: * Real code should preallocate exactly. */
59: PetscCall(MatSetOption(Asp, MAT_NEW_NONZERO_LOCATION_ERR, PETSC_FALSE));
61: /* Check zero rows */
62: PetscCall(MatGetOwnershipRange(A, &rstart, &rend));
63: nrows = 0;
64: for (row = rstart; row < rend; row++) {
65: PetscCall(MatGetRow(A, row, &ncols, &cols, &vals));
66: nnzA += ncols;
67: norm = 0.0;
68: for (j = 0; j < ncols; j++) {
69: val = PetscAbsScalar(vals[j]);
70: if (norm < val) norm = norm;
71: if (val > dtol) {
72: PetscCall(MatSetValues(Asp, 1, &row, 1, &cols[j], &vals[j], INSERT_VALUES));
73: nnzAsp++;
74: }
75: }
76: if (!norm) nrows++;
77: PetscCall(MatRestoreRow(A, row, &ncols, &cols, &vals));
78: }
79: PetscCall(MatAssemblyBegin(Asp, MAT_FINAL_ASSEMBLY));
80: PetscCall(MatAssemblyEnd(Asp, MAT_FINAL_ASSEMBLY));
82: percent = (PetscReal)nnzA * 100 / (m * n);
83: PetscCall(PetscPrintf(PETSC_COMM_SELF, " [%d] Matrix A local size %d,%d; nnzA %d, %g percent; No. of zero rows: %d\n", rank, m, n, nnzA, percent, nrows));
84: percent = (PetscReal)nnzAsp * 100 / (m * n);
85: PetscCall(PetscPrintf(PETSC_COMM_SELF, " [%d] Matrix Asp nnzAsp %d, %g percent\n", rank, nnzAsp, percent));
87: /* investigate matcoloring for Asp */
88: PetscBool Asp_coloring = PETSC_FALSE;
89: PetscCall(PetscOptionsHasName(NULL, NULL, "-Asp_color", &Asp_coloring));
90: if (Asp_coloring) {
91: MatColoring mc;
92: ISColoring iscoloring;
93: MatFDColoring matfdcoloring;
94: PetscCall(PetscPrintf(PETSC_COMM_WORLD, " Create coloring of Asp...\n"));
95: PetscCall(MatColoringCreate(Asp, &mc));
96: PetscCall(MatColoringSetType(mc, MATCOLORINGSL));
97: PetscCall(MatColoringSetFromOptions(mc));
98: PetscCall(MatColoringApply(mc, &iscoloring));
99: PetscCall(MatColoringDestroy(&mc));
100: PetscCall(MatFDColoringCreate(Asp, iscoloring, &matfdcoloring));
101: PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
102: PetscCall(MatFDColoringSetUp(Asp, iscoloring, matfdcoloring));
103: /*PetscCall(MatFDColoringView(matfdcoloring,PETSC_VIEWER_STDOUT_WORLD));*/
104: PetscCall(ISColoringDestroy(&iscoloring));
105: PetscCall(MatFDColoringDestroy(&matfdcoloring));
106: }
108: /* Write Asp in binary for study - see ~petsc/src/mat/tests/ex124.c */
109: PetscBool Asp_write = PETSC_FALSE;
110: PetscCall(PetscOptionsHasName(NULL, NULL, "-Asp_write", &Asp_write));
111: if (Asp_write) {
112: PetscViewer viewer;
113: PetscCall(PetscPrintf(PETSC_COMM_SELF, "Write Asp into file Asp.dat ...\n"));
114: PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, "Asp.dat", FILE_MODE_WRITE, &viewer));
115: PetscCall(MatView(Asp, viewer));
116: PetscCall(PetscViewerDestroy(&viewer));
117: }
119: PetscCall(MatDestroy(&A));
120: PetscCall(MatDestroy(&Asp));
121: PetscCall(PetscFinalize());
122: return 0;
123: }