Actual source code: genqmd.c
petsc-3.7.7 2017-09-25
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: /* */
47: PetscErrorCode SPARSEPACKgenqmd(const PetscInt *neqns,const PetscInt *xadj,const PetscInt *adjncy,
48: PetscInt *perm, PetscInt *invp, PetscInt *deg, PetscInt *marker,
49: PetscInt *rchset, PetscInt *nbrhd, PetscInt *qsize, PetscInt *qlink, PetscInt *nofsub)
50: {
51: /* System generated locals */
52: PetscInt i__1;
54: /* Local variables */
55: PetscInt ndeg, irch, node, nump1, j, inode;
56: PetscInt ip, np, mindeg, search;
57: PetscInt nhdsze, nxnode, rchsze, thresh, num;
59: /* INITIALIZE DEGREE VECTOR AND OTHER WORKING VARIABLES. */
62: /* Parameter adjustments */
63: --qlink;
64: --qsize;
65: --nbrhd;
66: --rchset;
67: --marker;
68: --deg;
69: --invp;
70: --perm;
71: --adjncy;
72: --xadj;
74: mindeg = *neqns;
75: *nofsub = 0;
76: i__1 = *neqns;
77: for (node = 1; node <= i__1; ++node) {
78: perm[node] = node;
79: invp[node] = node;
80: marker[node] = 0;
81: qsize[node] = 1;
82: qlink[node] = 0;
83: ndeg = xadj[node + 1] - xadj[node];
84: deg[node] = ndeg;
85: if (ndeg < mindeg) mindeg = ndeg;
86: }
87: num = 0;
88: /* PERFORM THRESHOLD SEARCH TO GET A NODE OF MIN DEGREE. */
89: /* VARIABLE SEARCH POINTS TO WHERE SEARCH SHOULD START. */
90: L200:
91: search = 1;
92: thresh = mindeg;
93: mindeg = *neqns;
94: L300:
95: nump1 = num + 1;
96: if (nump1 > search) search = nump1;
97: i__1 = *neqns;
98: for (j = search; j <= i__1; ++j) {
99: node = perm[j];
100: if (marker[node] < 0) goto L400;
101: ndeg = deg[node];
102: if (ndeg <= thresh) goto L500;
103: if (ndeg < mindeg) mindeg = ndeg;
104: L400:
105: ;
106: }
107: goto L200;
108: /* NODE HAS MINIMUM DEGREE. FIND ITS REACHABLE SETS BY */
109: /* CALLING QMDRCH. */
110: L500:
111: search = j;
112: *nofsub += deg[node];
113: marker[node] = 1;
114: SPARSEPACKqmdrch(&node, &xadj[1], &adjncy[1], °[1], &marker[1], &rchsze, &
115: rchset[1], &nhdsze, &nbrhd[1]);
116: /* ELIMINATE ALL NODES INDISTINGUISHABLE FROM NODE. */
117: /* THEY ARE GIVEN BY NODE, QLINK(NODE), .... */
118: nxnode = node;
119: L600:
120: ++num;
121: np = invp[nxnode];
122: ip = perm[num];
123: perm[np] = ip;
124: invp[ip] = np;
125: perm[num] = nxnode;
126: invp[nxnode] = num;
127: deg[nxnode] = -1;
128: nxnode = qlink[nxnode];
129: if (nxnode > 0) goto L600;
130: if (rchsze <= 0) goto L800;
132: /* UPDATE THE DEGREES OF THE NODES IN THE REACHABLE */
133: /* SET AND IDENTIFY INDISTINGUISHABLE NODES. */
134: SPARSEPACKqmdupd(&xadj[1], &adjncy[1], &rchsze, &rchset[1], °[1], &qsize[1], &
135: qlink[1], &marker[1], &rchset[rchsze + 1], &nbrhd[nhdsze + 1]);
137: /* RESET MARKER VALUE OF NODES IN REACH SET. */
138: /* UPDATE THRESHOLD VALUE FOR CYCLIC SEARCH. */
139: /* ALSO CALL QMDQT TO FORM NEW QUOTIENT GRAPH. */
140: marker[node] = 0;
141: i__1 = rchsze;
142: for (irch = 1; irch <= i__1; ++irch) {
143: inode = rchset[irch];
144: if (marker[inode] < 0) goto L700;
146: marker[inode] = 0;
147: ndeg = deg[inode];
148: if (ndeg < mindeg) mindeg = ndeg;
149: if (ndeg > thresh) goto L700;
150: mindeg = thresh;
151: thresh = ndeg;
152: search = invp[inode];
153: L700:
154: ;
155: }
156: if (nhdsze > 0) {
157: SPARSEPACKqmdqt(&node, &xadj[1], &adjncy[1], &marker[1], &rchsze, &rchset[1], &
158: nbrhd[1]);
159: }
160: L800:
161: if (num < *neqns) goto L300;
162: return(0);
163: }