Actual source code: sro.c
1: /*$Id: sro.c,v 1.26 2001/06/21 21:17:00 bsmith Exp $*/
3: #include src/mat/impls/baij/seq/baij.h
4: #include src/inline/spops.h
5: #include src/mat/impls/sbaij/seq/sbaij.h
6: #include petscsys.h
8: /*
9: This function is used before applying a
10: symmetric reordering to matrix A that is
11: in SBAIJ format.
13: The permutation is assumed to be symmetric, i.e.,
14: P = P^T (= inv(P)),
15: so the permuted matrix P*A*inv(P)=P*A*P^T is ensured to be symmetric.
17: The function is modified from sro.f of YSMP. The description from YSMP:
18: C THE NONZERO ENTRIES OF THE MATRIX M ARE ASSUMED TO BE STORED
19: C SYMMETRICALLY IN (IA,JA,A) FORMAT (I.E., NOT BOTH M(I,J) AND M(J,I)
20: C ARE STORED IF I NE J).
21: C
22: C SRO DOES NOT REARRANGE THE ORDER OF THE ROWS, BUT DOES MOVE
23: C NONZEROES FROM ONE ROW TO ANOTHER TO ENSURE THAT IF M(I,J) WILL BE
24: C IN THE UPPER TRIANGLE OF M WITH RESPECT TO THE NEW ORDERING, THEN
25: C M(I,J) IS STORED IN ROW I (AND THUS M(J,I) IS NOT STORED); WHEREAS
26: C IF M(I,J) WILL BE IN THE STRICT LOWER TRIANGLE OF M, THEN M(J,I) IS
27: C STORED IN ROW J (AND THUS M(I,J) IS NOT STORED).
30: -- output: new index set (inew, jnew) for A and a map a2anew that maps
31: values a to anew, such that all
32: nonzero A_(perm(i),iperm(k)) will be stored in the upper triangle.
33: Note: matrix A is not permuted by this function!
34: */
37: int MatReorderingSeqSBAIJ(Mat A,IS perm)
38: {
39: Mat_SeqSBAIJ *a=(Mat_SeqSBAIJ *)A->data;
40: int *r,ierr,i,mbs=a->mbs,*rip,*riip;
41: int *ai,*aj;
42: int *nzr,nz,jmin,jmax,j,k,ajk,len;
43: IS iperm; /* inverse of perm */
46: if (!mbs) return(0);
47: ISGetIndices(perm,&rip);
48: ISInvertPermutation(perm,PETSC_DECIDE,&iperm);
49: ISGetIndices(iperm,&riip);
51: for (i=0; i<mbs; i++) {
52: if (rip[i] != riip[i]) SETERRQ(1,"Non-symm. permutation, use symm. permutation or general matrix format");
53: }
54: ISRestoreIndices(iperm,&riip);
55: ISDestroy(iperm);
56:
57: if (!a->inew){
58: len = (mbs+1 + 2*(a->i[mbs]))*sizeof(int);
59: PetscMalloc(len,&ai);
60: aj = ai + mbs+1;
61: } else {
62: ai = a->inew; aj = a->jnew;
63: }
64: PetscMemcpy(ai,a->i,(mbs+1)*sizeof(int));
65: PetscMemcpy(aj,a->j,(a->i[mbs])*sizeof(int));
66:
67: /*
68: Phase 1: Find row index r in which to store each nonzero.
69: Initialize count of nonzeros to be stored in each row (nzr).
70: At the end of this phase, a nonzero a(*,*)=a(r(),aj())
71: s.t. a(perm(r),perm(aj)) will fall into upper triangle part.
72: */
74: PetscMalloc(mbs*sizeof(int),&nzr);
75: PetscMalloc(ai[mbs]*sizeof(int),&r);
76: for (i=0; i<mbs; i++) nzr[i] = 0;
77: for (i=0; i<ai[mbs]; i++) r[i] = 0;
78:
79: /* for each nonzero element */
80: for (i=0; i<mbs; i++){
81: nz = ai[i+1] - ai[i];
82: j = ai[i];
83: /* printf("nz = %d, j=%d\n",nz,j); */
84: while (nz--){
85: /* --- find row (=r[j]) and column (=aj[j]) in which to store a[j] ...*/
86: k = aj[j]; /* col. index */
87: /* printf("nz = %d, k=%d\n", nz,k); */
88: /* for entry that will be permuted into lower triangle, swap row and col. index */
89: if (rip[k] < rip[i]) aj[j] = i;
90: else k = i;
91:
92: r[j] = k; j++;
93: nzr[k] ++; /* increment count of nonzeros in that row */
94: }
95: }
97: /* Phase 2: Find new ai and permutation to apply to (aj,a).
98: Determine pointers (r) to delimit rows in permuted (aj,a).
99: Note: r is different from r used in phase 1.
100: At the end of this phase, (aj[j],a[j]) will be stored in
101: (aj[r(j)],a[r(j)]).
102: */
103: for (i=0; i<mbs; i++){
104: ai[i+1] = ai[i] + nzr[i];
105: nzr[i] = ai[i+1];
106: }
107:
108: /* determine where each (aj[j], a[j]) is stored in new (aj,a)
109: for each nonzero element (in reverse order) */
110: jmin = ai[0]; jmax = ai[mbs];
111: nz = jmax - jmin;
112: j = jmax-1;
113: while (nz--){
114: i = r[j]; /* row value */
115: if (aj[j] == i) r[j] = ai[i]; /* put diagonal nonzero at beginning of row */
116: else { /* put off-diagonal nonzero in last unused location in row */
117: nzr[i]--; r[j] = nzr[i];
118: }
119: j--;
120: }
121:
122: a->a2anew = aj + ai[mbs];
123: PetscMemcpy(a->a2anew,r,ai[mbs]*sizeof(int));
124:
125: /* Phase 3: permute (aj,a) to upper triangular form (wrt new ordering) */
126: for (j=jmin; j<jmax; j++){
127: while (r[j] != j){
128: k = r[j]; r[j] = r[k]; r[k] = k;
129: ajk = aj[k]; aj[k] = aj[j]; aj[j] = ajk;
130: /* ak = aa[k]; aa[k] = aa[j]; aa[j] = ak; */
131: }
132: }
133: ierr= ISRestoreIndices(perm,&rip);
135: a->inew = ai;
136: a->jnew = aj;
138: if (a->row) {
139: ISDestroy(a->row);
140: }
141: if (a->icol) {
142: ISDestroy(a->icol);
143: }
144: a->row = perm;
145: a->icol = perm;
146: PetscObjectReference((PetscObject)perm);
147: PetscObjectReference((PetscObject)perm);
149: PetscFree(nzr);
150: PetscFree(r);
151:
152: return(0);
153: }