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: PetscFunctionBegin;
58: /* Parameter adjustments */
59: --qlink;
60: --qsize;
61: --nbrhd;
62: --rchset;
63: --marker;
64: --deg;
65: --invp;
66: --perm;
67: --adjncy;
68: --xadj;
70: mindeg = *neqns;
71: *nofsub = 0;
72: i__1 = *neqns;
73: for (node = 1; node <= i__1; ++node) {
74: perm[node] = node;
75: invp[node] = node;
76: marker[node] = 0;
77: qsize[node] = 1;
78: qlink[node] = 0;
79: ndeg = xadj[node + 1] - xadj[node];
80: deg[node] = ndeg;
81: if (ndeg < mindeg) mindeg = ndeg;
82: }
83: num = 0;
84: /* PERFORM THRESHOLD SEARCH TO GET A NODE OF MIN DEGREE. */
85: /* VARIABLE SEARCH POINTS TO WHERE SEARCH SHOULD START. */
86: L200:
87: search = 1;
88: thresh = mindeg;
89: mindeg = *neqns;
90: L300:
91: nump1 = num + 1;
92: if (nump1 > search) search = nump1;
93: i__1 = *neqns;
94: for (j = search; j <= i__1; ++j) {
95: node = perm[j];
96: if (marker[node] < 0) goto L400;
97: ndeg = deg[node];
98: if (ndeg <= thresh) goto L500;
99: if (ndeg < mindeg) mindeg = ndeg;
100: L400:;
101: }
102: goto L200;
103: /* NODE HAS MINIMUM DEGREE. FIND ITS REACHABLE SETS BY */
104: /* CALLING QMDRCH. */
105: L500:
106: search = j;
107: *nofsub += deg[node];
108: marker[node] = 1;
109: PetscCall(SPARSEPACKqmdrch(&node, &xadj[1], &adjncy[1], °[1], &marker[1], &rchsze, &rchset[1], &nhdsze, &nbrhd[1]));
110: /* ELIMINATE ALL NODES INDISTINGUISHABLE FROM NODE. */
111: /* THEY ARE GIVEN BY NODE, QLINK(NODE), .... */
112: nxnode = node;
113: L600:
114: ++num;
115: np = invp[nxnode];
116: ip = perm[num];
117: perm[np] = ip;
118: invp[ip] = np;
119: perm[num] = nxnode;
120: invp[nxnode] = num;
121: deg[nxnode] = -1;
122: nxnode = qlink[nxnode];
123: if (nxnode > 0) goto L600;
124: if (rchsze <= 0) goto L800;
126: /* UPDATE THE DEGREES OF THE NODES IN THE REACHABLE */
127: /* SET AND IDENTIFY INDISTINGUISHABLE NODES. */
128: PetscCall(SPARSEPACKqmdupd(&xadj[1], &adjncy[1], &rchsze, &rchset[1], °[1], &qsize[1], &qlink[1], &marker[1], &rchset[rchsze + 1], &nbrhd[nhdsze + 1]));
130: /* RESET MARKER VALUE OF NODES IN REACH SET. */
131: /* UPDATE THRESHOLD VALUE FOR CYCLIC SEARCH. */
132: /* ALSO CALL QMDQT TO FORM NEW QUOTIENT GRAPH. */
133: marker[node] = 0;
134: i__1 = rchsze;
135: for (irch = 1; irch <= i__1; ++irch) {
136: inode = rchset[irch];
137: if (marker[inode] < 0) goto L700;
139: marker[inode] = 0;
140: ndeg = deg[inode];
141: if (ndeg < mindeg) mindeg = ndeg;
142: if (ndeg > thresh) goto L700;
143: mindeg = thresh;
144: thresh = ndeg;
145: search = invp[inode];
146: L700:;
147: }
148: if (nhdsze > 0) PetscCall(SPARSEPACKqmdqt(&node, &xadj[1], &adjncy[1], &marker[1], &rchsze, &rchset[1], &nbrhd[1]));
149: L800:
150: if (num < *neqns) goto L300;
151: PetscFunctionReturn(PETSC_SUCCESS);
152: }