Actual source code: slo.c
2: /* slo.f -- translated by f2c (version of 25 March 1992 12:58:56).*/
4: #include <../src/mat/color/impls/minpack/color.h>
6: PetscErrorCode MINPACKslo(PetscInt *n,const PetscInt * indrow,const PetscInt * jpntr,const PetscInt * indcol,const PetscInt *ipntr, PetscInt *ndeg,PetscInt * list,
7: PetscInt * maxclq,PetscInt *iwa1,PetscInt * iwa2,PetscInt * iwa3,PetscInt * iwa4)
8: {
9: /* System generated locals */
10: PetscInt i__1, i__2, i__3, i__4;
12: /* Local variables */
13: PetscInt jcol, ic, ip, jp, ir, mindeg, numdeg, numord;
15: /* Given the sparsity pattern of an m by n matrix A, this */
16: /* subroutine determines the smallest-last ordering of the */
17: /* columns of A. */
18: /* The smallest-last ordering is defined for the loopless */
19: /* graph G with vertices a(j), j = 1,2,...,n where a(j) is the */
20: /* j-th column of A and with edge (a(i),a(j)) if and only if */
21: /* columns i and j have a non-zero in the same row position. */
22: /* The smallest-last ordering is determined recursively by */
23: /* letting list(k), k = n,...,1 be a column with least degree */
24: /* in the subgraph spanned by the un-ordered columns. */
25: /* Note that the value of m is not needed by slo and is */
26: /* therefore not present in the subroutine statement. */
27: /* The subroutine statement is */
28: /* subroutine slo(n,indrow,jpntr,indcol,ipntr,ndeg,list, */
29: /* maxclq,iwa1,iwa2,iwa3,iwa4) */
30: /* where */
31: /* n is a positive integer input variable set to the number */
32: /* of columns of A. */
33: /* indrow is an integer input array which contains the row */
34: /* indices for the non-zeroes in the matrix A. */
35: /* jpntr is an integer input array of length n + 1 which */
36: /* specifies the locations of the row indices in indrow. */
37: /* The row indices for column j are */
38: /* indrow(k), k = jpntr(j),...,jpntr(j+1)-1. */
39: /* Note that jpntr(n+1)-1 is then the number of non-zero */
40: /* elements of the matrix A. */
41: /* indcol is an integer input array which contains the */
42: /* column indices for the non-zeroes in the matrix A. */
43: /* ipntr is an integer input array of length m + 1 which */
44: /* specifies the locations of the column indices in indcol. */
45: /* The column indices for row i are */
46: /* indcol(k), k = ipntr(i),...,ipntr(i+1)-1. */
47: /* Note that ipntr(m+1)-1 is then the number of non-zero */
48: /* elements of the matrix A. */
49: /* ndeg is an integer input array of length n which specifies */
50: /* the degree sequence. The degree of the j-th column */
51: /* of A is ndeg(j). */
52: /* list is an integer output array of length n which specifies */
53: /* the smallest-last ordering of the columns of A. The j-th */
54: /* column in this order is list(j). */
55: /* maxclq is an integer output variable set to the size */
56: /* of the largest clique found during the ordering. */
57: /* iwa1,iwa2,iwa3, and iwa4 are integer work arrays of length n. */
58: /* Subprograms called */
59: /* FORTRAN-supplied ... min */
60: /* Argonne National Laboratory. MINPACK Project. August 1984. */
61: /* Thomas F. Coleman, Burton S. Garbow, Jorge J. More' */
63: /* Parameter adjustments */
64: --iwa4;
65: --iwa3;
66: --iwa2;
67: --list;
68: --ndeg;
69: --ipntr;
70: --indcol;
71: --jpntr;
72: --indrow;
74: /* Function Body */
75: mindeg = *n;
76: i__1 = *n;
77: for (jp = 1; jp <= i__1; ++jp) {
78: iwa1[jp - 1] = 0;
79: iwa4[jp] = *n;
80: list[jp] = ndeg[jp];
81: /* Computing MIN */
82: i__2 = mindeg;
83: i__3 = ndeg[jp];
84: mindeg = PetscMin(i__2,i__3);
85: }
87: /* Create a doubly-linked list to access the degrees of the */
88: /* columns. The pointers for the linked list are as follows. */
90: /* Each un-ordered column ic is in a list (the degree list) */
91: /* of columns with the same degree. */
93: /* iwa1(numdeg) is the first column in the numdeg list */
94: /* unless iwa1(numdeg) = 0. In this case there are */
95: /* no columns in the numdeg list. */
97: /* iwa2(ic) is the column before ic in the degree list */
98: /* unless iwa2(ic) = 0. In this case ic is the first */
99: /* column in this degree list. */
101: /* iwa3(ic) is the column after ic in the degree list */
102: /* unless iwa3(ic) = 0. In this case ic is the last */
103: /* column in this degree list. */
105: /* If ic is an un-ordered column, then list(ic) is the */
106: /* degree of ic in the graph induced by the un-ordered */
107: /* columns. If jcol is an ordered column, then list(jcol) */
108: /* is the smallest-last order of column jcol. */
110: i__1 = *n;
111: for (jp = 1; jp <= i__1; ++jp) {
112: numdeg = ndeg[jp];
113: iwa2[jp] = 0;
114: iwa3[jp] = iwa1[numdeg];
115: if (iwa1[numdeg] > 0) {
116: iwa2[iwa1[numdeg]] = jp;
117: }
118: iwa1[numdeg] = jp;
119: }
120: *maxclq = 0;
121: numord = *n;
123: /* Beginning of iteration loop. */
125: L30:
127: /* Choose a column jcol of minimal degree mindeg. */
129: L40:
130: jcol = iwa1[mindeg];
131: if (jcol > 0) goto L50;
132: ++mindeg;
133: goto L40;
134: L50:
135: list[jcol] = numord;
137: /* Mark the size of the largest clique */
138: /* found during the ordering. */
140: if (mindeg + 1 == numord && !*maxclq) *maxclq = numord;
142: /* Termination test. */
144: --numord;
145: if (!numord) goto L80;
147: /* Delete column jcol from the mindeg list. */
149: iwa1[mindeg] = iwa3[jcol];
150: if (iwa3[jcol] > 0) iwa2[iwa3[jcol]] = 0;
152: /* Find all columns adjacent to column jcol. */
154: iwa4[jcol] = 0;
156: /* Determine all positions (ir,jcol) which correspond */
157: /* to non-zeroes in the matrix. */
159: i__1 = jpntr[jcol + 1] - 1;
160: for (jp = jpntr[jcol]; jp <= i__1; ++jp) {
161: ir = indrow[jp];
163: /* For each row ir, determine all positions (ir,ic) */
164: /* which correspond to non-zeroes in the matrix. */
166: i__2 = ipntr[ir + 1] - 1;
167: for (ip = ipntr[ir]; ip <= i__2; ++ip) {
168: ic = indcol[ip];
170: /* Array iwa4 marks columns which are adjacent to */
171: /* column jcol. */
173: if (iwa4[ic] > numord) {
174: iwa4[ic] = numord;
176: /* Update the pointers to the current degree lists. */
178: numdeg = list[ic];
179: --list[ic];
180: /* Computing MIN */
181: i__3 = mindeg;
182: i__4 = list[ic];
183: mindeg = PetscMin(i__3,i__4);
185: /* Delete column ic from the numdeg list. */
187: if (!iwa2[ic]) iwa1[numdeg] = iwa3[ic];
188: else iwa3[iwa2[ic]] = iwa3[ic];
190: if (iwa3[ic] > 0) iwa2[iwa3[ic]] = iwa2[ic];
192: /* Add column ic to the numdeg-1 list. */
194: iwa2[ic] = 0;
195: iwa3[ic] = iwa1[numdeg - 1];
196: if (iwa1[numdeg - 1] > 0) iwa2[iwa1[numdeg - 1]] = ic;
197: iwa1[numdeg - 1] = ic;
198: }
199: }
200: }
202: /* End of iteration loop. */
204: goto L30;
205: L80:
207: /* Invert the array list. */
209: i__1 = *n;
210: for (jcol = 1; jcol <= i__1; ++jcol) iwa2[list[jcol]] = jcol;
212: i__1 = *n;
213: for (jp = 1; jp <= i__1; ++jp) list[jp] = iwa2[jp];
214: return 0;
215: }