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,
 46:                                 PetscInt *perm, PetscInt *invp, PetscInt *deg, PetscInt *marker,
 47:                                 PetscInt *rchset, PetscInt *nbrhd, PetscInt *qsize, PetscInt *qlink, PetscInt *nofsub)
 48: {
 49:   /* System generated locals */
 50:   PetscInt i__1;

 52:   /* Local variables */
 53:   PetscInt ndeg, irch, node, nump1, j, inode;
 54:   PetscInt ip, np, mindeg, search;
 55:   PetscInt nhdsze, nxnode, rchsze, thresh, num;

 57: /*       INITIALIZE DEGREE VECTOR AND OTHER WORKING VARIABLES.   */

 59:   /* Parameter adjustments */
 60:   --qlink;
 61:   --qsize;
 62:   --nbrhd;
 63:   --rchset;
 64:   --marker;
 65:   --deg;
 66:   --invp;
 67:   --perm;
 68:   --adjncy;
 69:   --xadj;

 71:   mindeg  = *neqns;
 72:   *nofsub = 0;
 73:   i__1    = *neqns;
 74:   for (node = 1; node <= i__1; ++node) {
 75:     perm[node]   = node;
 76:     invp[node]   = node;
 77:     marker[node] = 0;
 78:     qsize[node]  = 1;
 79:     qlink[node]  = 0;
 80:     ndeg         = xadj[node + 1] - xadj[node];
 81:     deg[node]    = ndeg;
 82:     if (ndeg < mindeg) mindeg = ndeg;
 83:   }
 84:   num = 0;
 85: /*       PERFORM THRESHOLD SEARCH TO GET A NODE OF MIN DEGREE.   */
 86: /*       VARIABLE SEARCH POINTS TO WHERE SEARCH SHOULD START.    */
 87: L200:
 88:   search = 1;
 89:   thresh = mindeg;
 90:   mindeg = *neqns;
 91: L300:
 92:   nump1 = num + 1;
 93:   if (nump1 > search) search = nump1;
 94:   i__1 = *neqns;
 95:   for (j = search; j <= i__1; ++j) {
 96:     node = perm[j];
 97:     if (marker[node] < 0) goto L400;
 98:     ndeg = deg[node];
 99:     if (ndeg <= thresh) goto L500;
100:     if (ndeg < mindeg) mindeg = ndeg;
101: L400:
102:     ;
103:   }
104:   goto L200;
105: /*          NODE HAS MINIMUM DEGREE. FIND ITS REACHABLE SETS BY    */
106: /*          CALLING QMDRCH.                                        */
107: L500:
108:   search       = j;
109:   *nofsub     += deg[node];
110:   marker[node] = 1;
111:   SPARSEPACKqmdrch(&node, &xadj[1], &adjncy[1], &deg[1], &marker[1], &rchsze, &
112:                    rchset[1], &nhdsze, &nbrhd[1]);
113: /*          ELIMINATE ALL NODES INDISTINGUISHABLE FROM NODE.       */
114: /*          THEY ARE GIVEN BY NODE, QLINK(NODE), ....              */
115:   nxnode = node;
116: L600:
117:   ++num;
118:   np           = invp[nxnode];
119:   ip           = perm[num];
120:   perm[np]     = ip;
121:   invp[ip]     = np;
122:   perm[num]    = nxnode;
123:   invp[nxnode] = num;
124:   deg[nxnode]  = -1;
125:   nxnode       = qlink[nxnode];
126:   if (nxnode > 0) goto L600;
127:   if (rchsze <= 0) goto L800;

129: /*             UPDATE THE DEGREES OF THE NODES IN THE REACHABLE     */
130: /*             SET AND IDENTIFY INDISTINGUISHABLE NODES.            */
131:   SPARSEPACKqmdupd(&xadj[1], &adjncy[1], &rchsze, &rchset[1], &deg[1], &qsize[1], &
132:                    qlink[1], &marker[1], &rchset[rchsze + 1], &nbrhd[nhdsze + 1]);

134: /*             RESET MARKER VALUE OF NODES IN REACH SET.            */
135: /*             UPDATE THRESHOLD VALUE FOR CYCLIC SEARCH.            */
136: /*             ALSO CALL QMDQT TO FORM NEW QUOTIENT GRAPH.          */
137:   marker[node] = 0;
138:   i__1         = rchsze;
139:   for (irch = 1; irch <= i__1; ++irch) {
140:     inode = rchset[irch];
141:     if (marker[inode] < 0) goto L700;

143:     marker[inode] = 0;
144:     ndeg          = deg[inode];
145:     if (ndeg < mindeg) mindeg = ndeg;
146:     if (ndeg > thresh) goto L700;
147:     mindeg = thresh;
148:     thresh = ndeg;
149:     search = invp[inode];
150: L700:
151:     ;
152:   }
153:   if (nhdsze > 0) {
154:     SPARSEPACKqmdqt(&node, &xadj[1], &adjncy[1], &marker[1], &rchsze, &rchset[1], &
155:                     nbrhd[1]);
156:   }
157: L800:
158:   if (num < *neqns) goto L300;
159:   return 0;
160: }