Actual source code: sro.c
2: #include <../src/mat/impls/baij/seq/baij.h>
3: #include <../src/mat/impls/sbaij/seq/sbaij.h>
5: /*
6: This function is used before applying a
7: symmetric reordering to matrix A that is
8: in SBAIJ format.
10: The permutation is assumed to be symmetric, i.e.,
11: P = P^T (= inv(P)),
12: so the permuted matrix P*A*inv(P)=P*A*P^T is ensured to be symmetric.
13: - a wrong assumption! This code needs rework! -- Hong
15: The function is modified from sro.f of YSMP. The description from YSMP:
16: C THE NONZERO ENTRIES OF THE MATRIX M ARE ASSUMED TO BE STORED
17: C SYMMETRICALLY IN (IA,JA,A) FORMAT (I.E., NOT BOTH M(I,J) AND M(J,I)
18: C ARE STORED IF I NE J).
19: C
20: C SRO DOES NOT REARRANGE THE ORDER OF THE ROWS, BUT DOES MOVE
21: C NONZEROES FROM ONE ROW TO ANOTHER TO ENSURE THAT IF M(I,J) WILL BE
22: C IN THE UPPER TRIANGLE OF M WITH RESPECT TO THE NEW ORDERING, THEN
23: C M(I,J) IS STORED IN ROW I (AND THUS M(J,I) IS NOT STORED); WHEREAS
24: C IF M(I,J) WILL BE IN THE STRICT LOWER TRIANGLE OF M, THEN M(J,I) IS
25: C STORED IN ROW J (AND THUS M(I,J) IS NOT STORED).
27: -- output: new index set (inew, jnew) for A and a map a2anew that maps
28: values a to anew, such that all
29: nonzero A_(perm(i),iperm(k)) will be stored in the upper triangle.
30: Note: matrix A is not permuted by this function!
31: */
32: PetscErrorCode MatReorderingSeqSBAIJ(Mat A, IS perm)
33: {
34: Mat_SeqSBAIJ *a = (Mat_SeqSBAIJ *)A->data;
35: const PetscInt mbs = a->mbs;
37: if (!mbs) return 0;
38: SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Matrix reordering is not supported for sbaij matrix. Use aij format");
39: #if 0
40: const PetscInt *rip,*riip;
41: PetscInt *ai,*aj,*r;
42: PetscInt *nzr,nz,jmin,jmax,j,k,ajk,i;
43: IS iperm; /* inverse of perm */
44: ISGetIndices(perm,&rip);
46: ISInvertPermutation(perm,PETSC_DECIDE,&iperm);
47: ISGetIndices(iperm,&riip);
49: for (i=0; i<mbs; i++) {
51: }
52: ISRestoreIndices(iperm,&riip);
53: ISDestroy(&iperm);
55: if (!a->inew) {
56: PetscMalloc2(mbs+1,&ai, 2*a->i[mbs],&aj);
57: } else {
58: ai = a->inew; aj = a->jnew;
59: }
60: PetscArraycpy(ai,a->i,mbs+1);
61: PetscArraycpy(aj,a->j,a->i[mbs]);
63: /*
64: Phase 1: Find row index r in which to store each nonzero.
65: Initialize count of nonzeros to be stored in each row (nzr).
66: At the end of this phase, a nonzero a(*,*)=a(r(),aj())
67: s.t. a(perm(r),perm(aj)) will fall into upper triangle part.
68: */
70: PetscMalloc1(mbs,&nzr);
71: PetscMalloc1(ai[mbs],&r);
72: for (i=0; i<mbs; i++) nzr[i] = 0;
73: for (i=0; i<ai[mbs]; i++) r[i] = 0;
75: /* for each nonzero element */
76: for (i=0; i<mbs; i++) {
77: nz = ai[i+1] - ai[i];
78: j = ai[i];
79: /* printf("nz = %d, j=%d\n",nz,j); */
80: while (nz--) {
81: /* --- find row (=r[j]) and column (=aj[j]) in which to store a[j] ...*/
82: k = aj[j]; /* col. index */
83: /* printf("nz = %d, k=%d\n", nz,k); */
84: /* for entry that will be permuted into lower triangle, swap row and col. index */
85: if (rip[k] < rip[i]) aj[j] = i;
86: else k = i;
88: r[j] = k; j++;
89: nzr[k]++; /* increment count of nonzeros in that row */
90: }
91: }
93: /* Phase 2: Find new ai and permutation to apply to (aj,a).
94: Determine pointers (r) to delimit rows in permuted (aj,a).
95: Note: r is different from r used in phase 1.
96: At the end of this phase, (aj[j],a[j]) will be stored in
97: (aj[r(j)],a[r(j)]).
98: */
99: for (i=0; i<mbs; i++) {
100: ai[i+1] = ai[i] + nzr[i];
101: nzr[i] = ai[i+1];
102: }
104: /* determine where each (aj[j], a[j]) is stored in new (aj,a)
105: for each nonzero element (in reverse order) */
106: jmin = ai[0]; jmax = ai[mbs];
107: nz = jmax - jmin;
108: j = jmax-1;
109: while (nz--) {
110: i = r[j]; /* row value */
111: if (aj[j] == i) r[j] = ai[i]; /* put diagonal nonzero at beginning of row */
112: else { /* put off-diagonal nonzero in last unused location in row */
113: nzr[i]--; r[j] = nzr[i];
114: }
115: j--;
116: }
118: a->a2anew = aj + ai[mbs];
119: PetscArraycpy(a->a2anew,r,ai[mbs]);
121: /* Phase 3: permute (aj,a) to upper triangular form (wrt new ordering) */
122: for (j=jmin; j<jmax; j++) {
123: while (r[j] != j) {
124: k = r[j]; r[j] = r[k]; r[k] = k;
125: ajk = aj[k]; aj[k] = aj[j]; aj[j] = ajk;
126: /* ak = aa[k]; aa[k] = aa[j]; aa[j] = ak; */
127: }
128: }
129: ISRestoreIndices(perm,&rip);
131: a->inew = ai;
132: a->jnew = aj;
134: ISDestroy(&a->row);
135: ISDestroy(&a->icol);
136: PetscObjectReference((PetscObject)perm);
137: ISDestroy(&a->row);
138: a->row = perm;
139: PetscObjectReference((PetscObject)perm);
140: ISDestroy(&a->icol);
141: a->icol = perm;
143: PetscFree(nzr);
144: PetscFree(r);
145: return 0;
146: #endif
147: }