2 * A* Search - A search library used in Empire to determine paths between
4 * Copyright (C) 1990-1998 Phil Lapsley
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
24 #if !defined(lint) && !defined(SABER)
25 static char sccsid[] = "@(#)as_winnow.c 1.8 11/13/90";
28 static struct as_node *
29 as_newnode(struct as_node *backp, struct as_coord c,
30 double inclbcost, double lbcost, double knowncost, double seccost);
33 * Take a list of neighbor coordinates and winnow them down into
34 * an interesting list of neighbor nodes. This means:
37 * Compute a lower bound on the total cost to target.
38 * If this neighbor is already in our queue,
39 * See if the new neighbor is cheaper.
40 * If so, add it to queue and move the
41 * old node to the subsumed list.
42 * If not, ignore this neighbor.
43 * If this neighbor isn't in the queue, add it.
47 as_winnow(struct as_data *adp, struct as_coord *coords, int ncoords)
61 for (cp = coords, end = coords + ncoords; cp < end; cp++) {
63 incknowncost = (*adp->realcost)(adp->head->np->c, *cp,
65 knowncost = adp->head->np->knowncost + incknowncost;
67 * If this neighbor is already in the queue, we can
70 qp = as_iscinq(adp, *cp);
71 inclbcost = qp ? qp->np->inclbcost :
72 (*adp->lbcost)(*cp, adp->to, adp->userdata);
73 if (inclbcost < 0.0) /* skip bad cases */
75 lbcost = knowncost + inclbcost;
77 fprintf(stderr, "\tneighbor %d, %d, lbcost %f ", cp->x, cp->y, lbcost);
80 * If this neighbor is already in the queue, check to
81 * see which has the lower cost. If the one already in
82 * the queue is cheaper, skip this neighbor as bad. If
83 * the neighbor does, delete the one in the queue.
86 if (qp->np->lbcost <= lbcost) {
88 fprintf(stderr, "old, loses to %f\n", qp->np->lbcost);
93 fprintf(stderr, "old, wins over %f\n", qp->np->lbcost);
95 if (qp->np->flags & AS_TRIED) {
96 /* should "never happen" */
100 * The neighbor is better than a previously visited coordinate;
101 * remove the old coordinate from the queue and add it to
102 * the subsumed nodes queue. To get here at
103 * all we can't be the head, thus qp->prev is defined.
105 /* Delete from main queue */
106 qp->prev->next = qp->next;
108 qp->next->prev = qp->prev;
110 /* Add to subsumed queue */
112 adp->subsumed->prev = qp;
113 qp->next = adp->subsumed;
118 adp->subsumed->prev = NULL;
121 * At this point, the as_iscinq code may contain bogus pointer
122 * refs. They'll be fixed when as_merge merges the new
123 * neighbors into the main queue.
129 fprintf(stderr, "new\n");
134 seccost = qp->np->seccost;
136 seccost = (adp->seccost) ?
137 (*adp->seccost)(*cp, adp->to, adp->userdata) :
139 np = as_newnode(adp->head->np, *cp, inclbcost, lbcost,
145 fprintf(stderr, "Fixing pointer for %d, %d\n", adp->subsumed->np->c.x,
146 adp->subsumed->np->c.y);
148 adp->subsumed->np->back = np;
150 adp->neighbor_nodes[i++] = np;
153 adp->neighbor_nodes[i] = NULL;
159 static struct as_node *
160 as_newnode(struct as_node *backp, struct as_coord c,
161 double inclbcost, double lbcost, double knowncost, double seccost)
165 /* Got an interesting coordinate; make a node for it. */
166 AS_NEW_MALLOC(np, struct as_node, NULL);
169 np->inclbcost = inclbcost;
171 np->knowncost = knowncost;
172 np->seccost = seccost;
173 np->step = backp->step;