2 * Empire - A multi-player, client/server Internet based war game.
3 * Copyright (C) 1986-2014, Dave Pare, Jeff Bailey, Thomas Ruschak,
4 * Ken Stevens, Steve McClure, Markus Armbruster
6 * Empire 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 3 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, see <http://www.gnu.org/licenses/>.
21 * See files README, COPYING and CREDITS in the root of the source
22 * tree for related information and legal notices. It is expected
23 * that future projects/authors will amend these files as needed.
27 * pathfind.c: Find cheapest paths
29 * Known contributors to this file:
30 * Markus Armbruster, 2011
45 #ifdef PATH_FIND_DEBUG
46 #define DPRINTF(fmt, ...) ((void)printf(fmt , ## __VA_ARGS__))
48 #define DPRINTF(fmt, ...) ((void)0)
51 static char *bufrotate(char *buf, size_t bufsz, size_t i);
54 * Dijkstra's algorithm. Refer to your graph algorithm textbook for
55 * how it works. Implementation is specialized to hex maps.
57 * Define PATH_FIND_STATS for performance statistics on stdout.
61 * Array of sector data, indexed by sector uid
63 * We need to store a few values per sector visited by the path
64 * search. An array is the stupidest data structure that could
67 * Extra benefit: it works really well for distribution in a
68 * continental game, where we visit most sectors. That's our most
69 * demanding use of path search, and its performance has noticable
70 * impact on the update.
72 * Island game distribution is much less demanding. The array may not
73 * be the best choice here, but it's plainly good enough. Same for
74 * path searches outside the update.
79 * visit < pf_visit : unvisited, remaining members invalid
80 * visit == pf_visit : open, dir & cost tentative, heapi used
81 * visit == pf_visit + 1 : closed, dir & cost final, heapi unused
84 signed char dir; /* cheapest direction to source */
85 int heapi; /* index in heap, valid if open */
86 double cost; /* cost from source */
89 static unsigned short pf_visit;
90 static struct pf_map *pf_map;
93 * Binary heap, cost priority queue of all open sectors
95 * Again, we use the stupidest data structure that could possibly
96 * work: an array. And we make it so large it can hold *all* sectors.
97 * In practice, we need much less space, but a tighter upper bound is
98 * not obvious to me right now.
102 int uid; /* sector uid and */
103 coord x, y; /* coordinates, uid == XYOFFSET(x, y) */
104 double cost; /* cost from source */
107 static int pf_nheap; /* #entries in pf_nheap[] */
108 static struct pf_heap *pf_heap;
113 static coord pf_sx, pf_sy;
115 static natid pf_actor;
116 static double (*pf_sct_cost)(natid, int);
119 * Performance statistics
121 #ifdef PATH_FIND_STATS
122 static unsigned pf_nsearch, pf_nsource, pf_nopen, pf_nclose;
123 static unsigned pf_nheap_max, pf_noway;
124 static double pf_sumcost;
125 #define STAT_INC(v) ((void)((v)++))
126 #define STAT_INCBY(v, i) ((void)((v) += i))
127 #define STAT_HIMARK(v, h) ((void)((v) < (h) ? (v) = (h) : (h)))
128 #else /* !PATH_FIND_STATS */
129 #define STAT_INC(v) ((void)0)
130 #define STAT_INCBY(v, i) ((void)0)
131 #define STAT_HIMARK(v, h) ((void)0)
132 #endif /* !PATH_FIND_STATS */
134 #ifndef NDEBUG /* silence "not used" warning */
135 /* Is sector with uid UID open? */
139 return pf_map[uid].visit == pf_visit;
143 /* Is sector with uid UID closed? */
145 pf_is_closed(int uid)
148 * optimization: check > pf_visit instead of == pf_visit + 1
149 * works because pf_map[uid].visit <= pf_visit + 1
151 return pf_map[uid].visit > pf_visit;
154 /* Is sector with uid UID unvisited? */
156 pf_is_unvisited(int uid)
158 return pf_map[uid].visit < pf_visit;
161 #ifdef PATH_FIND_DEBUG
167 for (i = 0; i < pf_nheap; i++) {
168 uid = pf_heap[i].uid;
169 assert(0 <= uid && uid < WORLD_SZ());
170 assert(pf_map[uid].heapi == i);
171 assert(pf_map[uid].visit == pf_visit);
172 assert(pf_map[uid].cost <= pf_heap[i].cost);
174 assert(c >= pf_nheap || pf_heap[i].cost <= pf_heap[c].cost);
176 assert(c >= pf_nheap || pf_heap[i].cost <= pf_heap[c].cost);
179 for (uid = 0; uid < WORLD_SZ(); uid++) {
180 assert(pf_map[uid].visit <= pf_visit + 1);
181 if (pf_map[uid].visit == pf_visit) {
182 i = pf_map[uid].heapi;
183 assert(0 <= i && i < pf_nheap && pf_heap[i].uid == uid);
188 #define pf_check() ((void)0)
191 /* Swap pf_heap's I-th and J-th elements. */
193 pf_heap_swap(int i, int j)
197 assert(0 <= i && i < pf_nheap);
198 assert(0 <= j && j < pf_nheap);
200 pf_heap[i] = pf_heap[j];
202 pf_map[pf_heap[i].uid].heapi = i;
203 pf_map[pf_heap[j].uid].heapi = j;
206 /* Restore heap property after N-th element's cost increased. */
212 assert(0 <= n && n < pf_nheap);
213 for (r = n; (c = 2 * r + 1) < pf_nheap; r = c) {
214 if (c + 1 < pf_nheap && pf_heap[c].cost > pf_heap[c + 1].cost)
216 if (pf_heap[r].cost < pf_heap[c].cost)
222 /* Restore heap property after N-th element's cost decreased. */
228 assert(0 <= n && n < pf_nheap);
229 for (c = n; (p = (c - 1) / 2), c > 0; c = p) {
230 if (pf_heap[p].cost < pf_heap[c].cost)
237 * Open the unvisited sector X,Y.
238 * UID is sector uid, it equals XYOFFSET(X,Y).
239 * Cheapest path from source comes from direction DIR and has cost COST.
242 pf_open(int uid, coord x, coord y, int dir, double cost)
248 STAT_HIMARK(pf_nheap_max, (unsigned)pf_nheap);
249 DPRINTF("pf: open %d,%d %g %c %d\n", x, y, cost, dirch[dir], i);
250 assert(pf_is_unvisited(uid));
251 pf_map[uid].visit = pf_visit;
252 pf_map[uid].dir = dir;
253 pf_map[uid].heapi = i;
254 pf_map[uid].cost = cost;
255 pf_heap[i].uid = uid;
258 pf_heap[i].cost = cost;
265 * Close the sector at the top of the heap.
270 int uid = pf_heap[0].uid;
273 DPRINTF("pf: close %d,%d %d\n", pf_heap[0].x, pf_heap[0].y, pf_nheap);
274 assert(pf_is_open(uid));
276 pf_heap[0] = pf_heap[pf_nheap];
277 pf_map[pf_heap[0].uid].heapi = 0;
280 pf_map[uid].visit = pf_visit + 1;
284 /* silence "not used" warning */
285 #ifdef PATH_FIND_DEBUG
287 * Return cost from source to sector with uid UID.
288 * It must be visited, i.e. open or closed.
293 assert(!pf_is_unvisited(uid));
294 return pf_map[uid].cost;
299 x_in_dir(coord x, int dir)
303 assert(0 <= x && x < WORLD_X);
304 assert(0 <= dir && dir <= DIR_LAST);
305 xx = x + diroff[dir][0];
314 y_in_dir(coord y, int dir)
318 assert(0 <= y && y < WORLD_Y);
319 assert(0 <= dir && dir <= DIR_LAST);
320 yy = y + diroff[dir][1];
331 assert(DIR_FIRST <= dir && dir <= DIR_LAST);
332 return dir >= DIR_FIRST + 3 ? dir - 3 : dir + 3;
336 * Set the current source and cost function.
337 * SX,SY is the source.
338 * The cost to enter the sector with uid u is COST(ACTOR, u).
339 * Negative value means the sector can't be entered.
342 pf_set_source(coord sx, coord sy, natid actor, double (*cost)(natid, int))
344 STAT_INC(pf_nsource);
345 DPRINTF("pf: source %d,%d\n", sx, sy);
348 pf_suid = XYOFFSET(sx, sy);
353 pf_map = calloc(WORLD_SZ(), sizeof(*pf_map));
354 pf_heap = malloc(WORLD_SZ() * sizeof(*pf_heap));
356 } else if ((unsigned short)(pf_visit + 3) < pf_visit) {
357 DPRINTF("pf: visit wrap-around\n");
358 memset(pf_map, 0, WORLD_SZ() * sizeof(*pf_map));
365 pf_open(pf_suid, pf_sx, pf_sy, DIR_STOP, 0.0);
369 * Find cheapest path from current source to DX,DY, return its cost.
372 path_find_to(coord dx, coord dy)
378 STAT_INC(pf_nsearch);
379 DPRINTF("pf: dest %d,%d\n", dx, dy);
380 duid = XYOFFSET(dx, dy);
381 if (pf_is_closed(duid)) {
382 DPRINTF("pf: done old %g\n", pf_map[duid].cost);
383 STAT_INCBY(pf_sumcost, pf_map[duid].cost);
384 return pf_map[duid].cost;
387 while (pf_nheap > 0 && pf_heap[0].uid != duid) {
390 cost = pf_heap[0].cost;
393 for (i = 0; i < 6; i++) { /* for all neighbors */
394 nx = x_in_dir(x, DIR_FIRST + i);
395 ny = y_in_dir(y, DIR_FIRST + i);
396 nuid = XYOFFSET(nx, ny);
398 * Cost to enter NX,NY doesn't depend on direction of
399 * entry. This X,Y is at least as expensive as any
400 * previous one. Therefore, cost to go to NX,NY via X,Y
401 * is at least as high as any previously found route.
402 * Skip neighbors that have a route already.
404 if (!pf_is_unvisited(nuid))
406 c1 = pf_sct_cost(pf_actor, nuid);
409 pf_open(nuid, nx, ny, DIR_FIRST + i, cost + c1);
413 DPRINTF("pf: done new %g\n", !pf_nheap ? -1.0 : pf_map[duid].cost);
418 STAT_INCBY(pf_sumcost, pf_map[duid].cost);
419 return pf_map[duid].cost;
423 * Write route from SX,SY to DX,DY to BUF[BUFSIZ], return its length.
424 * If the route is longer than BUFSIZ-1 characters, it's truncated.
425 * You must compute path cost first, with path_find_to().
426 * SX,SY must be on a shortest path from the current source to DX,DY.
429 path_find_route(char *buf, size_t bufsz,
430 coord sx, coord sy, coord dx, coord dy)
436 suid = XYOFFSET(sx, sy);
437 assert(bufsz > 0 && !pf_is_unvisited(suid));
446 DPRINTF("pf: %d,%d %.*s%.*s\n",
448 (int)(bufsz - i), buf + i,
449 len >= bufsz ? (int)i : 0, buf);
450 uid = XYOFFSET(x, y);
451 assert(!pf_is_unvisited(uid));
453 if (d == DIR_STOP || uid == suid)
459 x = x_in_dir(x, rev_dir(d));
460 y = y_in_dir(y, rev_dir(d));
463 assert(x == sx && y == sy);
465 bufrotate(buf, bufsz, i);
467 assert(i + len < bufsz);
468 memmove(buf, buf + i, len + 1);
474 * Rotate BUF[BUFSZ] to put BUF[I] into BUF[0], and zero-terminate.
477 bufrotate(char *buf, size_t bufsz, size_t i)
483 n = MIN(i, sizeof(tmp));
485 memcpy(buf, buf + n, bufsz - n);
486 memcpy(buf + bufsz - n, tmp, n);
493 #ifdef PATH_FIND_DEBUG
495 path_find_visualize(coord sx, coord sy, coord dx, coord dy)
498 int xmin, xmax, ymin, ymax, x, y, odd, ch;
502 assert(pf_cost(XYOFFSET(sx, sy)) == 0.0);
503 c = pf_cost(XYOFFSET(dx, dy));
506 /* find bounding box */
509 for (y = -WORLD_Y / 2; y < WORLD_Y / 2; y++) {
510 odd = ((sx + -WORLD_X / 2) ^ (sy + y)) & 1;
511 for (x = -WORLD_X / 2 + odd; x < WORLD_X / 2; x += 2) {
512 uid = XYOFFSET(XNORM(sx + x), YNORM(sy + y));
513 if (pf_is_unvisited(uid))
525 printf("bbox %d:%d,%d:%d origin %d,%d\n",
526 xmin, xmax, ymin, ymax, sx, sy);
528 for (y = ymin; y <= ymax; y++) {
529 odd = ((sx + xmin) ^ (sy + y)) & 1;
532 for (x = xmin + odd; x <= xmax; x += 2) {
533 uid = XYOFFSET(XNORM(sx + x), YNORM(sy + y));
534 if (pf_is_unvisited(uid))
536 else if (uid == XYOFFSET(dx, dy))
538 else if (uid == XYOFFSET(sx, sy))
542 ch = cost > c ? '+' : '0' + (int)(10 * (cost / c));
548 path_find_route(buf, sizeof(buf), sx, sy, dx, dy);
549 printf("%s %g\n", buf, pf_cost(XYOFFSET(dx, dy)));
553 #ifdef PATH_FIND_STATS
555 path_find_print_stats(void)
557 printf("pathfind %u searches, %u sources, %u opened, %u closed,"
558 " %u heap max, %zu bytes, %u noway, %g avg cost\n",
559 pf_nsearch, pf_nsource, pf_nopen, pf_nclose,
561 (WORLD_SZ() * (sizeof(*pf_map) + sizeof(*pf_heap))),
562 pf_noway, pf_nsearch ? pf_sumcost / pf_nsearch : 0.0);
567 * Empire interface glue
571 cost_land(natid actor, int uid, int mobtype)
574 * Non-negative cost must not depend on ACTOR, see BestLandPath().
576 struct sctstr *sp = (void *)empfile[EF_SECTOR].cache;
578 if (sp[uid].sct_own != actor)
580 return sector_mcost(&sp[uid], mobtype);
584 cost_move(natid actor, int uid)
586 return cost_land(actor, uid, MOB_MOVE);
590 cost_march(natid actor, int uid)
592 return cost_land(actor, uid, MOB_MARCH);
596 cost_rail(natid actor, int uid)
598 return cost_land(actor, uid, MOB_RAIL);
602 cost_sail(natid actor, int uid)
604 struct sctstr *sp = (void *)empfile[EF_SECTOR].cache;
605 natid sctown = sp[uid].sct_own;
608 if (sctown && relations_with(sctown, actor) == ALLIED) {
609 /* FIXME duplicates shp_check_nav() logic */
610 switch (dchr[sp[uid].sct_type].d_nav) {
614 /* FIXME return 1.0 when all ships have M_CANAL */
617 return sp[uid].sct_effic >= 2 ? 1.0 : -1.0;
619 return sp[uid].sct_effic >= 60 ? 1.0 : -1.0;
625 bmap = ef_ptr(EF_BMAP, actor);
626 return bmap[uid] == '.' || bmap[uid] == ' ' || bmap[uid] == 0
631 cost_fly(natid actor, int uid)
636 static double (*cost_tab[])(natid, int) = {
637 cost_move, cost_march, cost_rail, cost_sail, cost_fly
641 * Start finding paths from SX,SY.
642 * Use mobility costs for ACTOR and MOBTYPE.
645 path_find_from(coord sx, coord sy, natid actor, int mobtype)
647 pf_set_source(sx, sy, actor, cost_tab[mobtype]);
651 * Find cheapest path from SX,SY to DX,DY, return its mobility cost.
652 * Use mobility costs for ACTOR and MOBTYPE.
655 path_find(coord sx, coord sy, coord dx, coord dy, natid actor, int mobtype)
657 pf_set_source(sx, sy, actor, cost_tab[mobtype]);
658 return path_find_to(dx, dy);