Actual source code: genqmd.c
2: /* genqmd.f -- translated by f2c (version 19931217).*/
4: #include <petscsys.h>
5: #include <petsc/private/matorderimpl.h>
7: /******************************************************************/
8: /*********** GENQMD ..... QUOT MIN DEGREE ORDERING **********/
9: /******************************************************************/
10: /* PURPOSE - THIS ROUTINE IMPLEMENTS THE MINIMUM DEGREE */
11: /* ALGORITHM. IT MAKES USE OF THE IMPLICIT REPRESENT- */
12: /* ATION OF THE ELIMINATION GRAPHS BY QUOTIENT GRAPHS, */
13: /* AND THE NOTION OF INDISTINGUISHABLE NODES. */
14: /* CAUTION - THE ADJACENCY VECTOR ADJNCY WILL BE */
15: /* DESTROYED. */
16: /* */
17: /* INPUT PARAMETERS - */
18: /* NEQNS - NUMBER OF EQUATIONS. */
19: /* (XADJ, ADJNCY) - THE ADJACENCY STRUCTURE. */
20: /* */
21: /* OUTPUT PARAMETERS - */
22: /* PERM - THE MINIMUM DEGREE ORDERING. */
23: /* INVP - THE INVERSE OF PERM. */
24: /* */
25: /* WORKING PARAMETERS - */
26: /* DEG - THE DEGREE VECTOR. DEG(I) IS NEGATIVE MEANS */
27: /* NODE I HAS BEEN NUMBERED. */
28: /* MARKER - A MARKER VECTOR, WHERE MARKER(I) IS */
29: /* NEGATIVE MEANS NODE I HAS BEEN MERGED WITH */
30: /* ANOTHER NODE AND THUS CAN BE IGNORED. */
31: /* RCHSET - VECTOR USED FOR THE REACHABLE SET. */
32: /* NBRHD - VECTOR USED FOR THE NEIGHBORHOOD SET. */
33: /* QSIZE - VECTOR USED TO STORE THE SIZE OF */
34: /* INDISTINGUISHABLE SUPERNODES. */
35: /* QLINK - VECTOR TO STORE INDISTINGUISHABLE NODES, */
36: /* I, QLINK(I), QLINK(QLINK(I)) ... ARE THE */
37: /* MEMBERS OF THE SUPERNODE REPRESENTED BY I. */
38: /* */
39: /* PROGRAM SUBROUTINES - */
40: /* QMDRCH, QMDQT, QMDUPD. */
41: /* */
42: /******************************************************************/
43: /* */
44: /* */
45: PetscErrorCode SPARSEPACKgenqmd(const PetscInt *neqns, const PetscInt *xadj, const PetscInt *adjncy, PetscInt *perm, PetscInt *invp, PetscInt *deg, PetscInt *marker, PetscInt *rchset, PetscInt *nbrhd, PetscInt *qsize, PetscInt *qlink, PetscInt *nofsub)
46: {
47: /* System generated locals */
48: PetscInt i__1;
50: /* Local variables */
51: PetscInt ndeg, irch, node, nump1, j, inode;
52: PetscInt ip, np, mindeg, search;
53: PetscInt nhdsze, nxnode, rchsze, thresh, num;
55: /* INITIALIZE DEGREE VECTOR AND OTHER WORKING VARIABLES. */
57: /* Parameter adjustments */
58: --qlink;
59: --qsize;
60: --nbrhd;
61: --rchset;
62: --marker;
63: --deg;
64: --invp;
65: --perm;
66: --adjncy;
67: --xadj;
69: mindeg = *neqns;
70: *nofsub = 0;
71: i__1 = *neqns;
72: for (node = 1; node <= i__1; ++node) {
73: perm[node] = node;
74: invp[node] = node;
75: marker[node] = 0;
76: qsize[node] = 1;
77: qlink[node] = 0;
78: ndeg = xadj[node + 1] - xadj[node];
79: deg[node] = ndeg;
80: if (ndeg < mindeg) mindeg = ndeg;
81: }
82: num = 0;
83: /* PERFORM THRESHOLD SEARCH TO GET A NODE OF MIN DEGREE. */
84: /* VARIABLE SEARCH POINTS TO WHERE SEARCH SHOULD START. */
85: L200:
86: search = 1;
87: thresh = mindeg;
88: mindeg = *neqns;
89: L300:
90: nump1 = num + 1;
91: if (nump1 > search) search = nump1;
92: i__1 = *neqns;
93: for (j = search; j <= i__1; ++j) {
94: node = perm[j];
95: if (marker[node] < 0) goto L400;
96: ndeg = deg[node];
97: if (ndeg <= thresh) goto L500;
98: if (ndeg < mindeg) mindeg = ndeg;
99: L400:;
100: }
101: goto L200;
102: /* NODE HAS MINIMUM DEGREE. FIND ITS REACHABLE SETS BY */
103: /* CALLING QMDRCH. */
104: L500:
105: search = j;
106: *nofsub += deg[node];
107: marker[node] = 1;
108: SPARSEPACKqmdrch(&node, &xadj[1], &adjncy[1], °[1], &marker[1], &rchsze, &rchset[1], &nhdsze, &nbrhd[1]);
109: /* ELIMINATE ALL NODES INDISTINGUISHABLE FROM NODE. */
110: /* THEY ARE GIVEN BY NODE, QLINK(NODE), .... */
111: nxnode = node;
112: L600:
113: ++num;
114: np = invp[nxnode];
115: ip = perm[num];
116: perm[np] = ip;
117: invp[ip] = np;
118: perm[num] = nxnode;
119: invp[nxnode] = num;
120: deg[nxnode] = -1;
121: nxnode = qlink[nxnode];
122: if (nxnode > 0) goto L600;
123: if (rchsze <= 0) goto L800;
125: /* UPDATE THE DEGREES OF THE NODES IN THE REACHABLE */
126: /* SET AND IDENTIFY INDISTINGUISHABLE NODES. */
127: SPARSEPACKqmdupd(&xadj[1], &adjncy[1], &rchsze, &rchset[1], °[1], &qsize[1], &qlink[1], &marker[1], &rchset[rchsze + 1], &nbrhd[nhdsze + 1]);
129: /* RESET MARKER VALUE OF NODES IN REACH SET. */
130: /* UPDATE THRESHOLD VALUE FOR CYCLIC SEARCH. */
131: /* ALSO CALL QMDQT TO FORM NEW QUOTIENT GRAPH. */
132: marker[node] = 0;
133: i__1 = rchsze;
134: for (irch = 1; irch <= i__1; ++irch) {
135: inode = rchset[irch];
136: if (marker[inode] < 0) goto L700;
138: marker[inode] = 0;
139: ndeg = deg[inode];
140: if (ndeg < mindeg) mindeg = ndeg;
141: if (ndeg > thresh) goto L700;
142: mindeg = thresh;
143: thresh = ndeg;
144: search = invp[inode];
145: L700:;
146: }
147: if (nhdsze > 0) SPARSEPACKqmdqt(&node, &xadj[1], &adjncy[1], &marker[1], &rchsze, &rchset[1], &nbrhd[1]);
148: L800:
149: if (num < *neqns) goto L300;
150: return 0;
151: }