Speed up A* neighbor cache hits

struct sctstr members sct_x, sct_y are normalized, no need to
normalize them again.

The neighbor cache now speeds up distribution path assembly by about
10% without the path cache, and by about 5% with the path cache.

src/lib/as/as_cache.c

@@ -58,6 +58,15 @@ static struct as_frompath **fromhead = (struct as_frompath **)0;
 
 static int as_cachepath_on = 0;	/* Default to off */
 
+#ifdef AS_STATS
+unsigned as_cache_tries, as_cache_hits;
+#define as_cache_try() ((void)as_cache_tries++)
+#define as_cache_hit() ((void)as_cache_hits++)
+#else
+#define as_cache_try() ((void)0)
+#define as_cache_hit() ((void)0)
+#endif
+
 void
 as_enable_cachepath(void)
 {
@@ -142,6 +151,13 @@ as_clear_cachepath(void)
     struct as_frompath *from, *from2;
     struct as_topath *to, *to2;
     int i, j;
+#ifdef AS_STATS
+    size_t index_sz = 0;
+    unsigned index_nb = 0, paths_nb = 0, paths = 0;
+#define stats_index(sz) ((void)(index_sz += (sz), index_nb++))
+#else
+#define stats_index(sz) ((void)0)
+#endif
 
     /* Cache not used yet :) */
     if (fromhead == NULL)
@@ -153,22 +169,43 @@ as_clear_cachepath(void)
 		for (to = from->tolist[i]; to; to = to2) {
 		    to2 = to->next;
 		    /* Free this path */
+#ifdef AS_STATS
+		    {
+			struct as_path *pp;
+			for (pp = to->path; pp; pp = pp->next)
+			    paths_nb++;
+			paths++;
+		    }
+#endif
 		    as_free_path(to->path);
 		    /* Free this node */
 		    free(to);
+		    stats_index(sizeof(*to));
 		}
 	    }
 	    /* Now, free the list of lists */
 	    free(from->tolist);
+	    stats_index(WORLD_Y * sizeof(*from->tolist));
 	    /* Save the next pointer */
 	    from2 = from->next;
 	    /* now, free this from node */
 	    free(from);
+	    stats_index(sizeof(*from));
 	}
     }
     /* Note we don't free the fromhead here, we just zero it.  That way,
        we can use it next time without mallocing int */
     memset(fromhead, 0, (sizeof(struct as_frompath *) * WORLD_Y));
+    stats_index(WORLD_Y * sizeof(*fromhead));
+#ifdef AS_STATS
+    fprintf(stderr, "as_cache %u searches, %u hits, %u entries,"
+	    " index %zu bytes %u blocks, paths %zu bytes %u blocks\n",
+	    as_cache_tries, as_cache_hits,
+	    paths,
+	    index_sz, index_nb,
+	    paths_nb * sizeof(struct as_path), paths_nb);
+    as_cache_hits = as_cache_tries = 0;
+#endif
 }
 
 struct as_path *
@@ -177,6 +214,7 @@ as_find_cachepath(coord fx, coord fy, coord tx, coord ty)
     struct as_frompath *from;
     struct as_topath *to;
 
+    as_cache_try();
     /* Is the cache on?  if not, return NULL */
     if (as_cachepath_on == 0)
 	return NULL;
@@ -189,8 +227,10 @@ as_find_cachepath(coord fx, coord fy, coord tx, coord ty)
     for (from = fromhead[fy]; from; from = from->next) {
 	if (from->x == fx) {
 	    for (to = from->tolist[ty]; to; to = to->next) {
-		if (to->x == tx)
+		if (to->x == tx) {
+		    as_cache_hit();
 		    return to->path;
+		}
 	    }
 	}
     }

src/lib/as/as_stats.c

@@ -31,8 +31,11 @@ as_stats(struct as_data *adp, FILE * fp)
     int i;
     int j;
     int total_q;
+    int total_p;
     int total_h;
+    size_t other;
     struct as_queue *qp;
+    struct as_path *pp;
     struct as_hash *hp;
 
     fprintf(fp, "Statistics:\n");
@@ -52,6 +55,10 @@ as_stats(struct as_data *adp, FILE * fp)
 	i++;
     fprintf(fp, "\tsubsumed:\t%d\n", i);
     total_q += i;
+    for (i = 0, pp = adp->path; pp; pp = pp->next)
+	i++;
+    total_p = i;
+    fprintf(fp, "path length: %d\n", total_p);
     fprintf(fp, "hash table statistics (size %d):\n", adp->hashsize);
     for (i = 0; i < adp->hashsize; i++) {
 	for (j = 0, hp = adp->hashtab[i]; hp; hp = hp->next)
@@ -64,10 +71,18 @@ as_stats(struct as_data *adp, FILE * fp)
     fprintf(fp, "\tqueues\t%d\n",
 	    (int)(total_q * sizeof(struct as_queue)));
     fprintf(fp, "\tnodes\t%d\n", (int)(total_q * sizeof(struct as_node)));
+    fprintf(fp, "\tpath\t%d\n", (int)(total_p * sizeof(struct as_path)));
     fprintf(fp, "\thash ents\t%d\n",
 	    (int)(total_h * sizeof(struct as_hash)));
+    other = sizeof(struct as_data);
+    other += adp->maxneighbors * sizeof(struct as_coord);
+    other += (adp->maxneighbors + 1) * sizeof(struct as_node *);
+    other += adp->hashsize * sizeof(struct as_hash *);
+    fprintf(fp, "\tother\t%d\n", (int)other);
     fprintf(fp, "\ttotal\t%d\n",
 	    (int)(total_q * sizeof(struct as_queue) +
 		  total_q * sizeof(struct as_node) +
-		  total_h * sizeof(struct as_hash)));
+		  total_p * sizeof(struct as_path) +
+		  total_h * sizeof(struct as_hash) +
+		  other));
 }

src/lib/common/path.c

@@ -26,7 +26,6 @@
  *  ---
  *
  *  path.c: Empire/A* Interface code.
- *          Define AS_STATS for A* statistics.
  *
  *  Known contributors to this file:
  *     Phil Lapsley, 1991
@@ -35,6 +34,18 @@
  *     Steve McClure, 1997
  */
 
+/*
+ * Define AS_STATS for A* statistics on stderr.
+ *
+ * Define AS_NO_PATH_CACHE to disable the path cache.  The path cache
+ * saves a lot of work, but uses lots of memory.  It should be a
+ * significant net win, unless you run out of memory.
+ *
+ * Define AS_NO_NEIGHBOR_CACHE to disable the neighbor cache.  The
+ * neighbor cache trades a modest amount of memory to save a bit of
+ * work.  In its current form, it doesn't really make a difference.
+ */
+
 #include <config.h>
 
 #include <stdio.h>
@@ -51,8 +62,6 @@
 #define BP_NEIGHBORS	6	/* max number of neighbors */
 
 struct bestp {
-    int sctcache_hits;
-    int sctcache_misses;
     int bp_mobtype;
     struct as_data *adp;
 };
@@ -82,8 +91,10 @@ bp_init(void)
     if (bp->adp == NULL)
 	return NULL;
 
+#ifndef AS_NO_NEIGHBOR_CACHE
     if (neighsects == NULL)
 	neighsects = calloc(WORLD_SZ() * 6, sizeof(struct sctstr *));
+#endif
 
     return bp;
 }
@@ -100,11 +111,16 @@ best_path(struct sctstr *from, struct sctstr *to, char *path, int mob_type)
     static struct bestp *mybestpath;
     struct as_data *adp;
     struct as_path *ap;
+    int res;
 
     if (!mybestpath)
 	mybestpath = bp_init();
     adp = mybestpath->adp;
+#ifdef AS_NO_PATH_CACHE
+    ap = NULL;
+#else
     ap = as_find_cachepath(from->sct_x, from->sct_y, to->sct_x, to->sct_y);
+#endif
     if (ap == NULL) {
 	adp->from.x = from->sct_x;
 	adp->from.y = from->sct_y;
@@ -112,22 +128,21 @@ best_path(struct sctstr *from, struct sctstr *to, char *path, int mob_type)
 	adp->to.y = to->sct_y;
 	mybestpath->bp_mobtype = mob_type;
 
-	if (as_search(adp) < 0)
+	res = as_search(adp);
+#ifdef AS_STATS
+	as_stats(adp, stderr);
+#ifndef AS_NO_NEIGHBOR_CACHE
+	fprintf(stderr, "neighbor cache %zu bytes\n",
+		WORLD_SZ() * 6 * sizeof(struct sctstr *));
+#endif
+#endif
+	if (res < 0)
 	    return -1;
 	ap = adp->path;
     }
 
     if (bp_path(ap, path) < 0)
 	return -1;
-
-#ifdef AS_STATS
-    as_stats(adp, stderr);
-#endif /* AS_STATS */
-#ifdef BP_STATS
-    fprintf(stderr, "best path %s\n", path);
-    fprintf(stderr, "cache hits/misses: %d/%d\n",
-	    bp->sctcache_hits, bp->sctcache_misses);
-#endif /* BP_STATS */
     return 0;
 }
 
@@ -212,8 +227,8 @@ bp_neighbors(struct as_coord c, struct as_coord *cp, void *pp)
 	    *ssp = sp;
 	} else {
 	    sp = *ssp;
-	    sx = XNORM(sp->sct_x);
+	    sx = sp->sct_x;
-	    sy = YNORM(sp->sct_y);
+	    sy = sp->sct_y;
 	}
 	/* No need to calculate cost each time, just make sure we can
 	   move through it.  We calculate it later. */
@@ -282,19 +297,25 @@ bp_coord_hash(struct as_coord c)
 void
 bp_enable_cachepath(void)
 {
+#ifndef AS_NO_PATH_CACHE
     as_enable_cachepath();
+#endif
 }
 
 void
 bp_disable_cachepath(void)
 {
+#ifndef AS_NO_PATH_CACHE
     as_disable_cachepath();
+#endif
 }
 
 void
 bp_clear_cachepath(void)
 {
+#ifndef AS_NO_PATH_CACHE
     as_clear_cachepath();
+#endif
 }
 
 double