1 #include <../src/mat/impls/baij/seq/baij.h>
2 #include <../src/mat/impls/sbaij/seq/sbaij.h>
3
4 /*
5 This function is used before applying a
6 symmetric reordering to matrix A that is
7 in SBAIJ format.
8
9 The permutation is assumed to be symmetric, i.e.,
10 P = P^T (= inv(P)),
11 so the permuted matrix P*A*inv(P)=P*A*P^T is ensured to be symmetric.
12 - a wrong assumption! This code needs rework! -- Hong
13
14 The function is modified from sro.f of YSMP. The description from YSMP:
15 C THE NONZERO ENTRIES OF THE MATRIX M ARE ASSUMED TO BE STORED
16 C SYMMETRICALLY IN (IA,JA,A) FORMAT (I.E., NOT BOTH M(I,J) AND M(J,I)
17 C ARE STORED IF I NE J).
18 C
19 C SRO DOES NOT REARRANGE THE ORDER OF THE ROWS, BUT DOES MOVE
20 C NONZEROES FROM ONE ROW TO ANOTHER TO ENSURE THAT IF M(I,J) WILL BE
21 C IN THE UPPER TRIANGLE OF M WITH RESPECT TO THE NEW ORDERING, THEN
22 C M(I,J) IS STORED IN ROW I (AND THUS M(J,I) IS NOT STORED); WHEREAS
23 C IF M(I,J) WILL BE IN THE STRICT LOWER TRIANGLE OF M, THEN M(J,I) IS
24 C STORED IN ROW J (AND THUS M(I,J) IS NOT STORED).
25
26 -- output: new index set (inew, jnew) for A and a map a2anew that maps
27 values a to anew, such that all
28 nonzero A_(perm(i),iperm(k)) will be stored in the upper triangle.
29 Note: matrix A is not permuted by this function!
30 */
MatReorderingSeqSBAIJ(Mat A,IS perm)31 PetscErrorCode MatReorderingSeqSBAIJ(Mat A, IS perm)
32 {
33 Mat_SeqSBAIJ *a = (Mat_SeqSBAIJ *)A->data;
34 const PetscInt mbs = a->mbs;
35
36 PetscFunctionBegin;
37 if (!mbs) PetscFunctionReturn(PETSC_SUCCESS);
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 PetscCall(ISGetIndices(perm,&rip));
45
46 PetscCall(ISInvertPermutation(perm,PETSC_DECIDE,&iperm));
47 PetscCall(ISGetIndices(iperm,&riip));
48
49 for (i=0; i<mbs; i++) PetscCheck(rip[i] == riip[i],PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Non-symmetric permutation, use symmetric permutation for symmetric matrices");
50 PetscCall(ISRestoreIndices(iperm,&riip));
51 PetscCall(ISDestroy(&iperm));
52
53 if (!a->inew) {
54 PetscCall(PetscMalloc2(mbs+1,&ai, 2*a->i[mbs],&aj));
55 } else {
56 ai = a->inew; aj = a->jnew;
57 }
58 PetscCall(PetscArraycpy(ai,a->i,mbs+1));
59 PetscCall(PetscArraycpy(aj,a->j,a->i[mbs]));
60
61 /*
62 Phase 1: Find row index r in which to store each nonzero.
63 Initialize count of nonzeros to be stored in each row (nzr).
64 At the end of this phase, a nonzero a(*,*)=a(r(),aj())
65 s.t. a(perm(r),perm(aj)) will fall into upper triangle part.
66 */
67
68 PetscCall(PetscMalloc1(mbs,&nzr));
69 PetscCall(PetscMalloc1(ai[mbs],&r));
70 for (i=0; i<mbs; i++) nzr[i] = 0;
71 for (i=0; i<ai[mbs]; i++) r[i] = 0;
72
73 /* for each nonzero element */
74 for (i=0; i<mbs; i++) {
75 nz = ai[i+1] - ai[i];
76 j = ai[i];
77 /* printf("nz = %d, j=%d\n",nz,j); */
78 while (nz--) {
79 /* --- find row (=r[j]) and column (=aj[j]) in which to store a[j] ...*/
80 k = aj[j]; /* col. index */
81 /* printf("nz = %d, k=%d\n", nz,k); */
82 /* for entry that will be permuted into lower triangle, swap row and col. index */
83 if (rip[k] < rip[i]) aj[j] = i;
84 else k = i;
85
86 r[j] = k; j++;
87 nzr[k]++; /* increment count of nonzeros in that row */
88 }
89 }
90
91 /* Phase 2: Find new ai and permutation to apply to (aj,a).
92 Determine pointers (r) to delimit rows in permuted (aj,a).
93 Note: r is different from r used in phase 1.
94 At the end of this phase, (aj[j],a[j]) will be stored in
95 (aj[r(j)],a[r(j)]).
96 */
97 for (i=0; i<mbs; i++) {
98 ai[i+1] = ai[i] + nzr[i];
99 nzr[i] = ai[i+1];
100 }
101
102 /* determine where each (aj[j], a[j]) is stored in new (aj,a)
103 for each nonzero element (in reverse order) */
104 jmin = ai[0]; jmax = ai[mbs];
105 nz = jmax - jmin;
106 j = jmax-1;
107 while (nz--) {
108 i = r[j]; /* row value */
109 if (aj[j] == i) r[j] = ai[i]; /* put diagonal nonzero at beginning of row */
110 else { /* put off-diagonal nonzero in last unused location in row */
111 nzr[i]--; r[j] = nzr[i];
112 }
113 j--;
114 }
115
116 a->a2anew = aj + ai[mbs];
117 PetscCall(PetscArraycpy(a->a2anew,r,ai[mbs]));
118
119 /* Phase 3: permute (aj,a) to upper triangular form (wrt new ordering) */
120 for (j=jmin; j<jmax; j++) {
121 while (r[j] != j) {
122 k = r[j]; r[j] = r[k]; r[k] = k;
123 ajk = aj[k]; aj[k] = aj[j]; aj[j] = ajk;
124 /* ak = aa[k]; aa[k] = aa[j]; aa[j] = ak; */
125 }
126 }
127 PetscCall(ISRestoreIndices(perm,&rip));
128
129 a->inew = ai;
130 a->jnew = aj;
131
132 PetscCall(ISDestroy(&a->row));
133 PetscCall(ISDestroy(&a->icol));
134 PetscCall(PetscObjectReference((PetscObject)perm));
135 PetscCall(ISDestroy(&a->row));
136 a->row = perm;
137 PetscCall(PetscObjectReference((PetscObject)perm));
138 PetscCall(ISDestroy(&a->icol));
139 a->icol = perm;
140
141 PetscCall(PetscFree(nzr));
142 PetscCall(PetscFree(r));
143 PetscFunctionReturn(PETSC_SUCCESS);
144 #endif
145 }
146