Compile-time option to use A* for distribution

Just for benchmarking.

Make.mk

@@ -119,7 +119,7 @@ obj := $(csrc:.c=.o) $(filter %.o, $(ac:.c=.o))
 # Dependencies:
 deps := $(obj:.o=.d)
 # Library archives:
-libs := $(addprefix lib/, libcommon.a libgen.a libglobal.a)
+libs := $(addprefix lib/, libcommon.a libas.a libgen.a libglobal.a)
 # Programs:
 util := $(addprefix src/util/, $(addsuffix $(EXEEXT), empdump empsched fairland files pconfig))
 client := src/client/empire$(EXEEXT)
@@ -291,6 +291,7 @@ $(client): $(filter src/client/%, $(obj)) src/lib/global/version.o
 
 $(util): $(libs)
 
+lib/libas.a: $(filter src/lib/as/%, $(obj))
 lib/libcommon.a: $(filter src/lib/common/%, $(obj))
 lib/libgen.a: $(filter src/lib/gen/%, $(obj))
 lib/libglobal.a: $(filter src/lib/global/%, $(obj))

include/path.h

@@ -67,6 +67,9 @@ extern int diroff[DIR_MAP+1][2];
 extern char dirch[DIR_MAP+2];
 extern char *routech[DIR_LAST+1];
 
+/* src/lib/common/bestpath.c */
+extern char *bestownedpath(char *, char *, int, int, int, int, int);
+
 /* src/lib/common/findpath.c */
 extern void path_find_from(coord, coord, natid, int);
 extern double path_find_to(coord, coord);
@@ -82,12 +85,16 @@ extern void path_find_print_stats(void);
 #endif
 
 /* src/lib/common/path.c */
+extern void bp_enable_cachepath(void);
+extern void bp_disable_cachepath(void);
+extern void bp_clear_cachepath(void);
 extern char *BestDistPath(char *, struct sctstr *, struct sctstr *,
 			  double *);
 extern char *BestLandPath(char *, struct sctstr *, struct sctstr *,
 			  double *, int);
 extern char *BestShipPath(char *, int, int, int, int, int);
 extern char *BestAirPath(char *, int, int, int, int);
+extern double pathcost(struct sctstr *, char *, int);
 
 /* src/lib/subs/paths.c */
 extern char *getpath(char *, char *, coord, coord, int, int, enum p_mode);

include/prototypes.h

@@ -253,6 +253,8 @@ int zdon(void);
 /*
  * src/lib/common/ *.c
  */
+/* bestpath.c */
+/* in path.h */
 /* conftab.c */
 extern int read_builtin_tables(void);
 extern int read_custom_tables(void);

src/lib/as/COPYRIGHT

@@ -0,0 +1,41 @@
+(Note that this copyright notice was changed with permission from Phil
+Lapsley to a copyright that complies with the GNU GPL.  The new
+copyright is supplied here, along with the old copyright notice
+below.)
+
+-----
+
+    A* Search - A search library used in Empire to determine paths between
+                objects.
+    Copyright (C) 1990-1998 Phil Lapsley
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+-----
+
+Old Copyright notice follows:
+
+"Copyright 1990 Phil Lapsley.  All rights reserved.
+
+Redistribution and use in source and binary forms for noncommercial
+purposes in support of BSD Empire are permitted provided that this
+notice is preserved and that due credit is given to the copyright
+holder.  This software is provided ``as is'' without express or implied
+warranty.  Entities interested in other distribution of this software
+should contact the copyright holder.
+
+(Phil is located at phil@east.berkeley.edu)"
+
+-----

src/lib/as/README

@@ -0,0 +1,300 @@
+Tue Nov 13 11:50:24 PST 1990	Phil Lapsley	phil@Berkeley.EDU
+
+This library implements a reasonably general version of the A* algorithm.
+Basically, A* is like an ordered search, but with a heuristic that allows
+it to make a better choices as to which path to take.  The subdirectory
+"test" has example code for using A* to search a weighted cartesian matrix.
+The file "XXX//bestpath.c" has code to interface Empire to the A*
+algorithms.
+
+This library is copyrighted; see the file COPYRIGHT for details.
+
+COMPILATION
+
+Do a "make" in this directory to make the library.  Cd into "test" and
+do a "make" there to make a test program, called (ta da) "test".
+
+LIBRARY USAGE
+
+Pretty much all the data that the user needs to communicate to the library
+is stored in an "as_data" structure, which is created by a call to "as_init":
+
+	struct as_data	*adp;
+
+	adp = as_init( ... );
+
+The arguments to as_init specify a number of key things the algorithm will
+use, and these are discussed below.
+
+Once you have an "as_data" structure, you can fill in its "from" and "to"
+members, which specify the coordinates of the points between which you want
+to go.  The basic coordinate data structure is the "as_coord", which is
+just an "x" integer and a "y" integer.  So:
+
+	adp->from.x = ...;
+	adp->from.y = ...;
+	adp->to.x = ...;
+	adp->to.y = ...;
+
+and then call as_search:
+
+	as_search(adp);
+
+If the return value of as_search is 0, the algorithm found a path from
+"from" to "to".  The path is stored in the "path" member of the "as_data"
+structure, and is just a linked list of coordinates ("as_coord" structs)
+from "from" to "to".
+
+If the return value of as_search is -1, the algorithm couldn't find a
+path from "from" to "to".  If the return is -2, a system error occurred
+(most probably malloc failed).
+
+After a call to as_search, lots of malloced data 'n' stuff will be
+floating around, all pointed to by items in the "as_data" data structure.
+If you call "as_search" again (presumably with new "from" and "to"
+coordinates), the system will free these data structures and reallocate
+new ones.  If you no longer want the data structures at all (i.e., you
+never intend to call "as_search" again), you can call:
+
+	as_delete(adp);
+
+and this will free up all data associated with the as_data structure pointed
+to by adp.
+
+ARGUMENTS TO AS_INIT
+
+"as_init" takes eight arguments, in the following order:
+
+	maxneighbors		The maximum number of neighboring sectors a
+				coordinate can have.  On a cartesian grid,
+				this would be 8.  On a hex map, it would be 6.
+
+	hashsize		The size of the hash table used to determine
+				if we've visited a particular coordinate.
+
+	hashfunc		A pointer to a function that takes an
+				"as_coord" as an argument and returns an
+				integer that will be used as a hash value.
+				If this is a NULL pointer, the as library
+				will assign its own hash function that just
+				adds the x and y coordinates together.
+
+	neighborfunc		A pointer to a function that takes a coordinate
+				(call it "c"), a pointer to an array of
+				coordinates of length "maxneighbors", and
+				a user data pointer (see below).  This
+				function should figure out the coordinates
+				of all the neighbors of "c" and put them in
+				the array cp[0] ... cp[maxneighbors-1].
+				It should then return the number of neighbors
+				found.
+
+	lbcostfunc		A pointer to a function that takes two
+				coordinates, call them "from" and "to",
+				and a user data pointer (see below).  It
+				returns a double precision *LOWER BOUND*
+				on the cost to get from "from" to "to".
+				"from" and "to" may be separated by an
+				arbitrary distance.  More on this below.
+
+	realcostfunc		A pointer to a function that takes two
+				coordinates, call them "from" and "to",
+				and a user data pointer (see below).  It
+				returns a double precision value of
+				the *actual cost* to move from "from" to
+				"to".  Note that "from" will never be more
+				than one sector away from "to".
+
+	seccostfunc		A pointer to a function that takes two
+				coordinates, call them "from" and "to",
+				and a user data pointer (see below).  It
+				returns a double precision value that will
+				be used to break ties when two nodes have
+				the same lower bound to the target.  An
+				example will be discussed below.
+
+	userdata		A (char *) that can be a pointer to
+				any kind of data you want.  This will
+				be passed as the third argument to the
+				neighborfunc, lbcostfunc, realcostfunc,
+				and seccostfunc.
+
+Look in test/cart.c to see examples of these functions for cartesian
+coordinates.
+
+NOTES ON THE LOWER BOUND FUNCTION
+
+"lbcostfunc" is *CRUCIAL* to the algorithm's performance.  The entire
+idea behind the A* algorithm is that, when considering whether to move
+to a new coordinate, you know two things:
+
+	(1) how much it's cost you to get to that coordinate so far,
+
+	(2) a LOWER BOUND on how much it will cost to get to the
+	    destination from that coordinate.
+
+If these two conditions are met, the algorithm will return the optimal
+path to the destination.  The closer the lower bound is to the actual
+cost to get from one point to another, the quicker the algorithm will
+find this path.  HOWEVER, if the lower bound is ever violated, i.e.,
+if the so-called lower bound function returns a value that is greater
+than the actual cost to get to the destination, then the algorithm will
+not necessarily find the optimal path.
+
+Example:
+
+Assume that we're on a cartesian matrix, and the cost to move from one point
+to another is just the distance between the two points, and that no
+other costs are involved.  In this case, the lower bound function could
+be the same as the actual cost function, i.e.,
+
+	real cost = lower bound cost = sqrt(dx^2 + dy^2);
+
+In this case, the algorithm will find the destination as quickly as possible.
+
+Another example:
+
+Again assume we're on a cartesian matrix, and the cost to move from
+one point to another is two things: (1) the distance between them, (2) some
+arbitrary cost function we get off of a map.  E.g.,
+
+		X
+
+	   0  1  2  3
+	0  0  0  0  0
+	1  0  0  0  0
+   Y	2  0  0  2  0
+	3  0  0  0  0
+
+The real cost to move from (x,y) 0,0 to 1,0 is 1.  That is, it's the distance
+(1) plus the value of the map at (1,0), which is 0.  The real cost to move
+from (1,2) to (2,2) is 3: the distance (1) plus the map value at (2,2), which
+is 2, totaling 3.
+
+In this case, the lower bound function could still be the distance between
+the two points, since this WILL NEVER BE MORE than the actual cost, and
+hence is a lower bound.  I.e.,
+
+	real cost = sqrt(dx^2 + dy^2) + map costs
+
+	lower bound cost = sqrt(dx^2 + dy^2)
+
+	lower bound cost <= real cost for all coordinates
+
+This is what the the example in the "test" directory uses.
+
+A third example:
+
+You could make the lower bound function always return 0.  This would be
+a valid lower bound of the cost to move between any two points.  In this
+case, the A* algorithm will behave like a breadth-first search, and isn't
+very much fun.
+
+SECONDARY COST FUNCTION
+
+The algorithm tries new coordinates in order of lowest lower-bound.
+There can be cases where the lower-bound function for two (or more)
+coordinates is the same, i.e., there is a tie.  The algorithm uses
+the secondary cost function (which does NOT have to be a lower bound)
+to choose which coordinate to pick.  A typical heuristic might be
+to use Euclidian distance for this secondary cost function, on the
+assumption that it's always better to move closer the destination.
+The Empire code does just this.
+
+If you don't need a secondary cost function, just specify a NULL pointer
+to the seccost argument to as_init, and the routines will use 0.0 for you.
+
+EMPIRE INTERFACE
+
+The interface code in "XXX/bestpath.c" is a rather complicated example
+of A* interface code.  What it does is based on some features of Empire
+that are explained here.
+
+First, movement cost in Empire is based on a quantity called "mobility
+cost", which is a property of every sector.  As we trace a path from
+source to destination, we add up mobility cost as we go.  Once we're
+there, we have a total mobility cost.  This is what we'd like to
+minimize.
+
+Second, Empire has highways, which are zero cost movement paths.  This
+hurts the A* algorithm, because it means that the lower bound cost
+function is very weak.  For example, think what happens if we move from
+one side of the country to another: if the two sectors are attached via
+a highway, the cost will be very small -- in fact, it will be the cost
+to move out of the source sector, and the cost to move into the
+destination sector.  If, on the other hand, the two sectors aren't
+connected by a highway, the cost could be quite large.  Thus, the lower
+bound is just the cost to move out of a sector plus the cost to move
+into a sector.  This is a pretty weak lower bound, and means that we
+have to explore a lot of sectors.
+
+Third, the mobility costs tend to tie a lot, as explained in the
+section above on secondary cost functions.  Thus, we use the Empire
+"mapdist" function as a secondary sort function to break ties.  For
+example, consider the case where a sector borders two highway sectors,
+one on each side.  The lower bound function will say that the two have
+equal lower bound costs, since they're both highways and cost nothing
+to move on.  The secondary sort function is then used to break the tie --
+it says, "Take the one that moves you closer to the destination".
+
+Fourth, all of the information we need about a sector (its mobility
+cost, who owns it, etc.) is stored in the sector file on disk.  This
+means that the getsect() function to get it off disk will do a read(),
+which is VERY expensive.  Because of the weak lower bound, A* ends up
+checking lots of sectors, including sectors that it's seen before.
+To avoid doing thousands of system calls per second, the bestpath.c file
+has sector caching routines that store in memory copies of every
+sector we read.  (The function bp_getsect handles this).  This means
+we never read a sector from disk more than once, although at the expense
+of using lots of memory.
+
+THEORY OF OPERATION
+
+The basic idea is as follows:
+
+	1. Add the start node to the head of a master queue.
+	2. Is the head of the queue where we want to be?  If so, stop.
+	3. Make a list of all the neighbors coordinates around the
+	   coordinate of the head.
+
+	4. For each neighbor coordinate,
+
+		Compute the lower bound cost to the destination from here.
+
+		If this coordinate is already on the either the
+		master queue or the "tried" queue:
+
+		4a.	If it was on either the "master" queue or the
+			"tried" queue and the one on the queue has a
+			smaller lower-bound than the neighbor, ignore
+			this neighbor and go on to the next neighbor.
+
+		4b.	If it was on the "master" queue and the new
+			neighbor has a smaller lower bound,
+				Move the one on the queue to a different
+				queue called "subsumed".
+
+		4c.	If it was on the "tried" queue and the new
+			neighbor has a smaller lower bound,
+				Move the one on the "tried" queue to the
+				master queue, and update its lower bound
+				value to be as the new neighbor, and
+				update its backpointer appropriately.
+
+	   We now have a list of all neighbor coordinates that are either
+	   not on the queue already, or are cheaper than the ones on the
+	   queue.
+
+	5. Move the node at the head of the queue (the one whose neighbors
+	   we now have in a list) onto a different queue called "tried".
+
+	6. Sort this list of neighbors, and merge it into the master queue,
+	   keeping the master queue ordered by lower bound cost to destination.
+
+	7. Goto 2.
+
+My algorithm does all of this, plus a little more (the above doesn't really
+mention backpointers except in passing), EXCEPT: I don't do step 4c.
+I'm not convinced that this can ever occur if the lower bound rule isn't
+broken, and I have yet to see it occur.  However, if as_winnow returns -1,
+this error has occurred.

src/lib/as/as.h

@@ -0,0 +1,195 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+/*
+ * A* definitions.
+ *
+ * @(#)as.h	1.9	11/13/90
+ */
+/*
+ * 11/09/98 - Steve McClure
+ *  Added path list caching structures
+ */
+
+#ifndef AS_H
+#define AS_H
+
+#include <stdio.h>
+#include "types.h"
+
+/*
+ * Coordinate.
+ */
+struct as_coord {
+    int x, y;
+};
+
+/*
+ * Path, made up of a linked list of coordinates.
+ */
+struct as_path {
+    struct as_coord c;
+    struct as_path *next;
+};
+
+/*
+ * Basic node, used internally by A* algorithm.
+ */
+struct as_node {
+    struct as_coord c;		/* our coordinate */
+    double knowncost;		/* cost so far  */
+    double lbcost;		/* lower bound on cost to dest */
+    double inclbcost;		/* incremental lower bound cost */
+    double seccost;		/* used to break ties */
+    int step;
+    int flags;
+    struct as_node *back;
+};
+#define AS_TRIED	1	/* we've tried this node before */
+
+/*
+ * Linked list of nodes, used internally by A* algorithm.
+ */
+struct as_queue {
+    struct as_node *np;
+    struct as_queue *next;
+    struct as_queue *prev;
+};
+
+/*
+ * Hash table entry, used to determine if we've seen a particular
+ * coordinate before.
+ */
+struct as_hash {
+    struct as_coord c;
+    struct as_queue *qp;
+    struct as_hash *next;
+};
+
+/*
+ * User's handle on A*, returned by as_init().  Some of the data here is
+ * used by A* internals.
+ */
+struct as_data {
+    int maxneighbors;		/* max # of neighbors a cell can have */
+    int hashsize;		/* size of internal hash table */
+
+    /* hash function (coord -> int) */
+    int (*hash)(struct as_coord);
+    /* function to find neighbors */
+    int (*neighbor)(struct as_coord, struct as_coord *, void *);
+    /* function to give lower bound cost */
+    double (*lbcost)(struct as_coord, struct as_coord, void *);
+    /* function to give real cost */
+    double (*realcost)(struct as_coord, struct as_coord, void *);
+    /* function to secondary cost */
+    double (*seccost)(struct as_coord, struct as_coord, void *);
+    void *userdata;		/* user's data, passed to callbacks */
+    struct as_coord from;	/* from coordinate */
+    struct as_coord to;		/* to coordinate */
+    struct as_path *path;	/* solution */
+
+    /* below are "private" to as_ routines */
+    struct as_queue *head;
+    struct as_queue *tried;
+    struct as_hash **hashtab;
+    struct as_queue *subsumed;
+    struct as_coord *neighbor_coords;
+    struct as_node **neighbor_nodes;
+};
+
+/*
+ * Added these for caching of paths as we stumble across them
+ */
+
+struct as_topath {
+    coord x;
+    struct as_path *path;	/* Path from holder of this list to here */
+    struct as_topath *next;
+};
+
+struct as_frompath {
+    coord x;
+    struct as_topath **tolist;	/* List of nodes we have a path to */
+    struct as_frompath *next;
+};
+
+/*
+ * Some cheezy allocation macros.
+ */
+#define AS_NEW_ARRAY(p, type, n, err) \
+	(p) = (type *)calloc((n), sizeof(*(p))); \
+	if ((p) == NULL) \
+		return err; \
+
+#define AS_NEW(p, type, err) \
+	AS_NEW_ARRAY((p), type, 1, err);
+
+#define AS_NEW_MALLOC(p, type, err) \
+	(p) = (type *)malloc(sizeof(type)); \
+	if ((p) == NULL) \
+	       return err; \
+
+/* Functions that the user can call.  */
+
+extern struct as_data *as_init(int maxneighbors, int hashsize,
+			       int (*hashfunc)(struct as_coord),
+			       int (*neighborfunc)(struct as_coord,
+						   struct as_coord *,
+						   void *),
+			       double (*lbcostfunc)(struct as_coord,
+						    struct as_coord,
+						    void *),
+			       double (*realcostfunc)(struct as_coord,
+						      struct as_coord,
+						      void *),
+			       double (*seccostfunc)(struct as_coord,
+						     struct as_coord,
+						     void *),
+			       void *userdata);
+extern int as_search(struct as_data *adp);
+extern void as_delete(struct as_data *adp);
+extern void as_reset(struct as_data *adp);
+extern void as_stats(struct as_data *adp, FILE * fp);
+extern struct as_path *as_find_cachepath(coord fx, coord fy,
+					 coord tx, coord ty);
+
+/* Functions that are "private" to algorithm */
+
+extern void as_add_cachepath(struct as_data *adp);
+extern void as_clear_cachepath(void);
+extern void as_enable_cachepath(void);
+extern void as_disable_cachepath(void);
+
+extern void as_makepath(struct as_data *adp);
+extern void as_free_path(struct as_path *pp);
+
+extern int as_costcomp(const void *, const void *);
+extern struct as_queue *as_extend(struct as_data *adp);
+extern struct as_queue *as_merge(struct as_data *adp,
+				 struct as_queue *head,
+				 struct as_node **neighbors);
+extern struct as_queue *as_iscinq(struct as_data *adp, struct as_coord c);
+extern void as_setcinq(struct as_data *adp,
+		       struct as_coord c, struct as_queue *qp);
+extern void as_free_hashtab(struct as_data *adp);
+extern int as_winnow(struct as_data *adp,
+		     struct as_coord *coords, int ncoords);
+
+#endif

src/lib/as/as_cache.c

@@ -0,0 +1,238 @@
+/*
+ *  Empire - A multi-player, client/server Internet based war game.
+ *  Copyright (C) 1986-2010, Dave Pare, Jeff Bailey, Thomas Ruschak,
+ *                           Ken Stevens, Steve McClure
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *  ---
+ *
+ *  See files README, COPYING and CREDITS in the root of the source
+ *  tree for related information and legal notices.  It is expected
+ *  that future projects/authors will amend these files as needed.
+ *
+ *  ---
+ *
+ *  as_cache.c: Routines used to create/delete caches of A* paths.
+ *
+ *  Known contributors to this file:
+ *     Steve McClure, 1998
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include "as.h"
+#include "optlist.h"
+
+/* The way this works is interesting. :) */
+/* We keep a pointer to a list of pointers.  The index into this list
+ * is the y coordinate of the from sector.  This member points to a list
+ * of from sectors on that y coordinate.  So, we march that list checking
+ * the x value to find the from x,y we want. */
+/* Once we find the from x,y, that node has the same type of pointer to
+ * a list of pointers.  The index into this list is the y coordinate of
+ * the to sector.  This member points to a list of to sectors on that y
+ * coordinate.  So, we march that list checking the x value to find the
+ * to x,y we want. */
+/* These lists are dynamically created since the world is dynamically sized. */
+/* See, I told you it was interesting. :) */
+
+static struct as_frompath **fromhead = (struct as_frompath **)0;
+
+/* Note that we only want to cache during updates.  Other times, it
+ * probably doesn't make much sense, but can be done. */
+
+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)
+{
+    as_cachepath_on = 1;
+}
+
+void
+as_disable_cachepath(void)
+{
+    as_cachepath_on = 0;
+}
+
+/* Note we want these to be as fast as possible */
+
+void
+as_add_cachepath(struct as_data *adp)
+{
+    struct as_frompath *from;
+    struct as_topath *to = (struct as_topath *)0;
+    struct as_node *np;
+
+    /* Don't do anything if we aren't cacheing these */
+    if (as_cachepath_on == 0)
+	return;
+
+    /* Note we will only allocate this once.  Afterwards, we just keep
+     * zeroing it since it's rather small and we don't need to re-allocate
+     * each time. */
+    if (fromhead == NULL) {
+	fromhead = calloc(1, sizeof(struct as_frompath *) * WORLD_Y);
+	if (fromhead == NULL)
+	    return;
+    }
+
+    np = adp->head->np;
+    for (from = fromhead[adp->from.y]; from; from = from->next)
+	if (from->x == adp->from.x)
+	    break;
+    if (from) {
+	for (to = from->tolist[np->c.y]; to; to = to->next) {
+	    if (to->x == np->c.x) {
+		/* It is already here!  Don't bother adding it again */
+		return;
+	    }
+	}
+    } else {
+	/* We must make a new one of these */
+	from = malloc(sizeof(struct as_frompath));
+	if (from == NULL)
+	    return;
+	/* And set some stuff */
+	from->x = adp->from.x;
+	/* Here we malloc a whole bunch of tolist pointers. */
+	from->tolist = calloc(1, sizeof(struct as_topath *) * WORLD_Y);
+	/* Now, add from to the global list */
+	from->next = fromhead[adp->from.y];
+	fromhead[adp->from.y] = from;
+    }
+    if (!to) {
+	/* We must make a new one */
+	to = malloc(sizeof(struct as_topath));
+	/* We can't, sorry */
+	if (to == NULL)
+	    return;
+	/* Now set some stuff */
+	to->x = np->c.x;
+	/* Now add it to the list we are in */
+	to->next = from->tolist[np->c.y];
+	from->tolist[np->c.y] = to;
+    }
+    /* Now, make the path */
+    as_makepath(adp);
+    /* Now, take the path */
+    to->path = adp->path;
+    /* And clear the path in the adp */
+    adp->path = NULL;
+}
+
+void
+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)
+	return;
+
+    for (j = 0; j < WORLD_Y; j++) {
+	for (from = fromhead[j]; from; from = from2) {
+	    for (i = 0; i < WORLD_Y; i++) {
+		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 *
+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;
+
+    /* Do we have any cached? */
+    if (fromhead == NULL)
+	return NULL;
+
+    /* Yes! */
+    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) {
+		    as_cache_hit();
+		    return to->path;
+		}
+	    }
+	}
+    }
+    return NULL;
+}

src/lib/as/as_costcomp.c

@@ -0,0 +1,50 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <config.h>
+
+#include "as.h"
+
+/*
+ * Compare the lower bound costs of two nodes.  If the two nodes have
+ * equal lower bound costs, sort on the secondary field.
+ * Used as comparision function for qsort.
+ */
+int
+as_costcomp(const void *p1, const void *p2)
+{
+    struct as_node *const *n1 = p1;
+    struct as_node *const *n2 = p2;
+    double diff;
+
+    diff = (*n1)->lbcost - (*n2)->lbcost;
+    if (diff < -0.0001)
+	return -1;
+    if (diff > 0.0001)
+	return 1;
+
+    /* equal, check secondary cost */
+    diff = (*n1)->seccost - (*n2)->seccost;
+    if (diff < -0.0001)
+	return -1;
+    if (diff > 0.0001)
+	return 1;
+    return 0;
+}

src/lib/as/as_delete.c

@@ -0,0 +1,85 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include "as.h"
+
+static void as_free_queue(struct as_queue *queue);
+
+/*
+ * Free any dynamically allocated data stored in the as_data structure.
+ */
+void
+as_reset(struct as_data *adp)
+{
+    as_free_queue(adp->head);
+    adp->head = NULL;
+    as_free_queue(adp->tried);
+    adp->tried = NULL;
+    as_free_queue(adp->subsumed);
+    adp->subsumed = NULL;
+    as_free_hashtab(adp);
+    as_free_path(adp->path);
+    adp->path = NULL;
+}
+
+/*
+ * Free a queue (either the main, subsumed, or tried).
+ */
+static void
+as_free_queue(struct as_queue *queue)
+{
+    struct as_queue *qp, *qp2;
+
+    for (qp = queue; qp; qp = qp2) {
+	free(qp->np);
+	qp2 = qp->next;
+	free(qp);
+    }
+}
+
+/*
+ * Free a path.
+ */
+void
+as_free_path(struct as_path *pp)
+{
+    struct as_path *pp2;
+
+    for (; pp; pp = pp2) {
+	pp2 = pp->next;
+	free(pp);
+    }
+}
+
+/*
+ * Delete the as_data structure (which includes freeing its data).
+ */
+void
+as_delete(struct as_data *adp)
+{
+    as_reset(adp);
+    free(adp->neighbor_coords);
+    free(adp->neighbor_nodes);
+    free(adp->hashtab);
+    free(adp);
+}

src/lib/as/as_extend.c

@@ -0,0 +1,71 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include "as.h"
+
+/*
+ * Extend the queue by neighbors.  This entails getting the
+ * coordinates of all the neighbors, figuring out their lower bound
+ * costs, throwing away ones that are more expensive than ones we
+ * already have, sorting, tand then merging into the queue.
+ */
+struct as_queue *
+as_extend(struct as_data *adp)
+{
+    struct as_queue *qp;
+    int i;
+    struct as_queue *head;
+
+    head = adp->head;
+
+    /* Find the neighboring coordinates. */
+    i = adp->neighbor(head->np->c, adp->neighbor_coords, adp->userdata);
+    if (i == 0)
+	return NULL;
+    /*
+     * Get rid of neighbors that are more costly than ones we already have,
+     * and sort the rest into an array of as_nodes.
+     */
+    i = as_winnow(adp, adp->neighbor_coords, i);
+    if (i < 0)
+	return NULL;
+    if (i > 1)
+	qsort(adp->neighbor_nodes, i,
+	      sizeof(*adp->neighbor_nodes), as_costcomp);
+
+    /* remove old coord from head of queue and add to list of tried */
+    qp = head;
+    head = head->next;
+    if (head)
+	head->prev = NULL;
+    if (adp->tried) {
+	adp->tried->prev = qp;
+	qp->next = adp->tried;
+	adp->tried = qp;
+    } else
+	adp->tried = qp;
+    adp->tried->np->flags |= AS_TRIED;
+
+    head = as_merge(adp, head, adp->neighbor_nodes);
+    return head;
+}

src/lib/as/as_hash.c

@@ -0,0 +1,83 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include "as.h"
+
+/*
+ * Return a pointer to the as_queue structure associated with
+ * this coordinate if the coordinate is in the queue.
+ */
+struct as_queue *
+as_iscinq(struct as_data *adp, struct as_coord c)
+{
+    int hashval;
+    struct as_hash *hp;
+
+    hashval = adp->hash(c) % adp->hashsize;
+
+    for (hp = adp->hashtab[hashval]; hp; hp = hp->next)
+	if (hp->c.x == c.x && hp->c.y == c.y)
+	    return hp->qp;
+
+    return NULL;
+}
+
+/*
+ * Set the queue structure associated with this coordinate.
+ */
+void
+as_setcinq(struct as_data *adp, struct as_coord c, struct as_queue *qp)
+{
+    int hashval;
+    struct as_hash *hp;
+    struct as_hash *new;
+
+    new = (struct as_hash *)malloc(sizeof(struct as_hash));
+    new->c = c;
+    new->qp = qp;
+
+    hashval = adp->hash(c) % adp->hashsize;
+    hp = adp->hashtab[hashval];
+
+    new->next = (hp) ? hp : NULL;
+    adp->hashtab[hashval] = new;
+}
+
+/*
+ * Walk down the hash table array, freeing the chains and zeroing
+ * the chain pointers.
+ */
+void
+as_free_hashtab(struct as_data *adp)
+{
+    int i;
+    struct as_hash *hp, *hp2;
+
+    for (i = 0; i < adp->hashsize; i++) {
+	for (hp = adp->hashtab[i]; hp; hp = hp2) {
+	    hp2 = hp->next;
+	    free(hp);
+	}
+	adp->hashtab[i] = NULL;
+    }
+}

src/lib/as/as_init.c

@@ -0,0 +1,59 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include "as.h"
+
+/*
+ * Return an as_data structure with the necessary fields filled in
+ * and space malloced.  Return NULL if malloc fails.
+ */
+struct as_data *
+as_init(int maxneighbors,
+	int hashsize,
+	int (*hashfunc)(struct as_coord),
+	int (*neighborfunc)(struct as_coord, struct as_coord *, void *),
+	double (*lbcostfunc)(struct as_coord, struct as_coord, void *),
+	double (*realcostfunc)(struct as_coord, struct as_coord, void *),
+	double (*seccostfunc)(struct as_coord, struct as_coord, void *),
+	void *userdata)
+{
+    struct as_data *adp;
+
+    AS_NEW(adp, struct as_data, NULL);
+    AS_NEW_ARRAY(adp->neighbor_coords, struct as_coord,
+		 maxneighbors, NULL);
+    AS_NEW_ARRAY(adp->neighbor_nodes, struct as_node *,
+		 maxneighbors + 1, NULL);
+    AS_NEW_ARRAY(adp->hashtab, struct as_hash *, hashsize, NULL);
+
+    adp->maxneighbors = maxneighbors;
+    adp->hashsize = hashsize;
+    adp->hash = hashfunc;
+    adp->neighbor = neighborfunc;
+    adp->lbcost = lbcostfunc;
+    adp->realcost = realcostfunc;
+    adp->seccost = seccostfunc;
+    adp->userdata = userdata;
+
+    return adp;
+}

src/lib/as/as_merge.c

@@ -0,0 +1,83 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include "as.h"
+
+/*
+ * Merge neighbors into queue, keeping it sorted.  "neighbors" is sorted,
+ * both by lower bound cost and then by secondary cost.
+ */
+struct as_queue *
+as_merge(struct as_data *adp, struct as_queue *head,
+	 struct as_node **neighbors)
+{
+    struct as_queue *qp;
+    struct as_queue *pp;	/* previous pointer */
+    struct as_queue *ip;	/* insert pointer */
+    struct as_node *np;
+    int i;
+
+    qp = head;
+    pp = NULL;
+    for (i = 0; neighbors[i]; i++) {
+	np = neighbors[i];
+	/* scan until qp points to a node we should go in front of */
+	while (qp && (qp->np->lbcost < np->lbcost)) {
+	    pp = qp;
+	    qp = qp->next;
+	}
+	/* check for equal lower bounds, and use secondary cost if = */
+	if (qp && qp->np->lbcost == np->lbcost) {
+	    while (qp && (qp->np->lbcost == np->lbcost) &&
+		   (qp->np->seccost < np->seccost)) {
+		pp = qp;
+		qp = qp->next;
+	    }
+	}
+	AS_NEW_MALLOC(ip, struct as_queue, NULL);
+	/* if there was such a node, insert us in front of it */
+	if (qp) {
+	    ip->prev = qp->prev;
+	    if (ip->prev)
+		ip->prev->next = ip;
+	    ip->next = qp;
+	    qp->prev = ip;
+	    if (qp == head)
+		head = ip;
+	} else {		/* otherwise add us to end of queue */
+	    ip->next = NULL;
+	    ip->prev = pp;
+	    if (ip->prev)
+		ip->prev->next = ip;
+	    else {
+		head = ip;
+	    }
+	    pp = ip;
+	}
+	ip->np = np;
+	as_setcinq(adp, np->c, ip);
+	np->step++;
+    }
+
+    return head;
+}

src/lib/as/as_search.c

@@ -0,0 +1,146 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+/*
+ * 11/09/98 - Steve McClure
+ *  Added path list caching structures
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include "as.h"
+
+/*
+ * Basic A* search function.  "adp" should have been initialized by
+ * as_init (any previously allocated data will be freed by as_reset here),
+ * and adp->from and adp->to should be set accordingly.  On success,
+ * returns 0, with adp->path set to a linked list of coordinates to target.
+ * If we can't find target, return -1; if malloc fails, return -2.
+ */
+int
+as_search(struct as_data *adp)
+{
+    int iter = 0;
+    struct as_queue *head;
+    struct as_node *np;
+#ifdef DEBUG
+    int i;
+    struct as_queue *qp;
+    struct as_path *pp;
+#endif /* DEBUG */
+
+    as_reset(adp);
+
+    /*
+     * Jump start the queue by making first element the zero-cost
+     * node where we start.
+     */
+    AS_NEW_MALLOC(head, struct as_queue, -2);
+    adp->head = head;
+    head->next = head->prev = NULL;
+    AS_NEW(np, struct as_node, -2);
+    np->c = adp->from;
+    head->np = np;
+    as_setcinq(adp, head->np->c, adp->head);
+
+    for (;;) {
+	iter++;
+	/* see if we're done, one way or another */
+	if (head == NULL)
+	    break;
+
+#ifdef DEBUG
+	fprintf(stderr, "Iteration %d, head at %d, %d\n", iter,
+		head->np->c.x, head->np->c.y);
+#endif /* DEBUG */
+
+	/* Add it to the cache */
+	as_add_cachepath(adp);
+
+	if (head->np->c.x == adp->to.x && head->np->c.y == adp->to.y)
+	    break;
+
+	/* extend queue by neighbors */
+#ifdef DEBUG
+	fprintf(stderr, "\tExtending queue\n");
+#endif /* DEBUG */
+	adp->head = head = as_extend(adp);
+	/* FIXME leaks when as_extend() returns NULL without adding to tried */
+
+#ifdef DEBUG
+	fprintf(stderr, "queue:\n");
+	i = 0;
+	for (qp = head; qp; qp = qp->next) {
+	    fprintf(stderr, "\t%d, %d so far %f lb %f sec %f\n",
+		    qp->np->c.x, qp->np->c.y,
+		    qp->np->knowncost, qp->np->lbcost, qp->np->seccost);
+	    i++;
+	}
+	fprintf(stderr, "\tqueue len %d\n", i);
+#endif /* DEBUG */
+
+    }
+
+    if (head == NULL) {
+#ifdef DEBUG
+	fprintf(stderr, "Failed\n");
+#endif /* DEBUG */
+	return -1;
+    }
+
+    as_makepath(adp);
+
+#ifdef DEBUG
+    fprintf(stderr, "Succeeded, iter %d, cost %f!\n", iter,
+	    head->np->knowncost);
+    fprintf(stderr, "Path:\n");
+    for (pp = adp->path; pp; pp = pp->next) {
+	fprintf(stderr, "\t%d, %d\n", pp->c.x, pp->c.y);
+    }
+    fprintf(stderr, "Tried queue:\n");
+    for (qp = adp->tried; qp; qp = qp->next) {
+	fprintf(stderr, "\t%d, %d\n", qp->np->c.x, qp->np->c.y);
+    }
+    fprintf(stderr, "Subsumed queue:\n");
+    for (qp = adp->subsumed; qp; qp = qp->next) {
+	fprintf(stderr, "\t%d, %d\n", qp->np->c.x, qp->np->c.y);
+    }
+#endif /* DEBUG */
+
+    return 0;
+}
+
+/*
+ * Work backwards through the list of nodes (starting at head)
+ * to produce a path.
+ */
+void
+as_makepath(struct as_data *adp)
+{
+    struct as_path *pp;
+    struct as_node *np;
+
+    for (np = adp->head->np; np; np = np->back) {
+	pp = malloc(sizeof(struct as_path));
+	pp->c = np->c;
+	pp->next = adp->path;
+	adp->path = pp;
+    }
+}

src/lib/as/as_stats.c

@@ -0,0 +1,88 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <config.h>
+
+#include "as.h"
+
+/*
+ * Print statistics on algorithm performance to the file pointer "fp".
+ */
+void
+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");
+
+    fprintf(fp, "queue lengths:\n");
+    total_q = 0;
+    total_h = 0;
+    for (i = 0, qp = adp->head; qp; qp = qp->next)
+	i++;
+    fprintf(fp, "\tmain:\t%d\n", i);
+    total_q += i;
+    for (i = 0, qp = adp->tried; qp; qp = qp->next)
+	i++;
+    fprintf(fp, "\ttried:\t%d\n", i);
+    total_q += i;
+    for (i = 0, qp = adp->subsumed; qp; qp = qp->next)
+	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)
+	    j++;
+	fprintf(fp, "\t%d\t%d\n", i, j);
+	total_h += j;
+    }
+    fprintf(fp, "\ttotal\t%d\n", total_h);
+    fprintf(fp, "approximate memory usage (bytes):\n");
+    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_p * sizeof(struct as_path) +
+		  total_h * sizeof(struct as_hash) +
+		  other));
+}

src/lib/as/as_winnow.c

@@ -0,0 +1,174 @@
+/*
+ *  A* Search - A search library used in Empire to determine paths between
+ *              objects.
+ *  Copyright (C) 1990-1998 Phil Lapsley
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include "as.h"
+
+static struct as_node *as_newnode(struct as_node *backp, struct as_coord c,
+				  double inclbcost, double lbcost,
+				  double knowncost, double seccost);
+
+/*
+ * Take a list of neighbor coordinates and winnow them down into
+ * an interesting list of neighbor nodes.  This means:
+ *
+ *	For each neighbor,
+ *		Compute a lower bound on the total cost to target.
+ *		If this neighbor is already in our queue,
+ *			See if the new neighbor is cheaper.
+ *			If so, add it to queue and move the
+ *			old node to the subsumed list.
+ *			If not, ignore this neighbor.
+ *		If this neighbor isn't in the queue, add it.
+ */
+int
+as_winnow(struct as_data *adp, struct as_coord *coords, int ncoords)
+{
+    int i = 0;
+    int fix_pointer;
+    double knowncost;
+    double incknowncost;
+    double lbcost;
+    double inclbcost;
+    double seccost;
+    struct as_coord *cp;
+    struct as_coord *end;
+    struct as_queue *qp;
+    struct as_node *np;
+
+    for (cp = coords, end = coords + ncoords; cp < end; cp++) {
+	fix_pointer = 0;
+	incknowncost = adp->realcost(adp->head->np->c, *cp, adp->userdata);
+	knowncost = adp->head->np->knowncost + incknowncost;
+	/*
+	 * If this neighbor is already in the queue, we can
+	 * save some time.
+	 */
+	qp = as_iscinq(adp, *cp);
+	inclbcost = qp ? qp->np->inclbcost :
+	    adp->lbcost(*cp, adp->to, adp->userdata);
+	if (inclbcost < 0.0)	/* skip bad cases */
+	    continue;
+	lbcost = knowncost + inclbcost;
+#ifdef DEBUG
+	fprintf(stderr, "\tneighbor %d, %d, lbcost %f ", cp->x, cp->y,
+		lbcost);
+#endif /* DEBUG */
+	/*
+	 * If this neighbor is already in the queue, check to
+	 * see which has the lower cost.  If the one already in
+	 * the queue is cheaper, skip this neighbor as bad.  If
+	 * the neighbor does, delete the one in the queue.
+	 */
+	if (qp) {
+	    if (qp->np->lbcost <= lbcost) {
+#ifdef DEBUG
+		fprintf(stderr, "old, loses to %f\n", qp->np->lbcost);
+#endif /* DEBUG */
+		continue;
+	    } else {
+#ifdef DEBUG
+		fprintf(stderr, "old, wins over %f\n", qp->np->lbcost);
+#endif /* DEBUG */
+		if (qp->np->flags & AS_TRIED) {
+		    /* should "never happen" */
+		    return 0;
+		}
+		/*
+		 * The neighbor is better than a previously visited coordinate;
+		 * remove the old coordinate from the queue and add it to
+		 * the subsumed nodes queue.  To get here at
+		 * all we can't be the head, thus qp->prev is defined.
+		 */
+		/* Delete from main queue */
+		qp->prev->next = qp->next;
+		if (qp->next)
+		    qp->next->prev = qp->prev;
+
+		/* Add to subsumed queue */
+		if (adp->subsumed) {
+		    adp->subsumed->prev = qp;
+		    qp->next = adp->subsumed;
+		} else {
+		    qp->next = NULL;
+		}
+		adp->subsumed = qp;
+		adp->subsumed->prev = NULL;
+		fix_pointer = 1;
+		/*
+		 * At this point, the as_iscinq code may contain bogus pointer
+		 * refs.  They'll be fixed when as_merge merges the new
+		 * neighbors into the main queue.
+		 */
+	    }
+	}
+#ifdef DEBUG
+	else {
+	    fprintf(stderr, "new\n");
+	}
+#endif /* DEBUG */
+
+	if (qp)
+	    seccost = qp->np->seccost;
+	else
+	    seccost = adp->seccost ?
+		adp->seccost(*cp, adp->to, adp->userdata) : 0.0;
+	np = as_newnode(adp->head->np, *cp, inclbcost, lbcost,
+			knowncost, seccost);
+	if (np == NULL)
+	    return 0;
+	if (fix_pointer) {
+#ifdef DEBUG
+	    fprintf(stderr, "Fixing pointer for %d, %d\n",
+		    adp->subsumed->np->c.x, adp->subsumed->np->c.y);
+#endif
+	    adp->subsumed->np->back = np;
+	}
+	adp->neighbor_nodes[i++] = np;
+
+    }
+    adp->neighbor_nodes[i] = NULL;
+
+    return i;
+}
+
+
+static struct as_node *
+as_newnode(struct as_node *backp, struct as_coord c,
+	   double inclbcost, double lbcost, double knowncost,
+	   double seccost)
+{
+    struct as_node *np;
+
+    /* Got an interesting coordinate; make a node for it. */
+    AS_NEW_MALLOC(np, struct as_node, NULL);
+    np->flags = 0;
+    np->c = c;
+    np->inclbcost = inclbcost;
+    np->lbcost = lbcost;
+    np->knowncost = knowncost;
+    np->seccost = seccost;
+    np->step = backp->step;
+    np->back = backp;
+
+    return np;
+}

src/lib/common/bestpath.c

@@ -0,0 +1,223 @@
+/*
+ *  Empire - A multi-player, client/server Internet based war game.
+ *  Copyright (C) 1986-2011, Dave Pare, Jeff Bailey, Thomas Ruschak,
+ *                Ken Stevens, Steve McClure, Markus Armbruster
+ *
+ *  Empire is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *  ---
+ *
+ *  See files README, COPYING and CREDITS in the root of the source
+ *  tree for related information and legal notices.  It is expected
+ *  that future projects/authors will amend these files as needed.
+ *
+ *  ---
+ *
+ *  bestpath.c: Find the best path between sectors
+ *
+ *  Known contributors to this file:
+ *     Steve McClure, 1998-2000
+ *     Markus Armbruster, 2006
+ */
+
+/*
+ * IMPORTANT: These routines are very selectively used in the server.
+ *
+ * "bestownedpath" is only used to determine paths for ships and planes.
+ *
+ * Callers should not be calling these directly anymore. They should use
+ * the "BestShipPath", "BestAirPath", "BestLandPath" and "BestDistPath"
+ * functions.  Note that those last two use the A* algorithms to find
+ * information.
+ */
+
+#include <config.h>
+
+#include "file.h"
+#include "misc.h"
+#include "nat.h"
+#include "optlist.h"
+#include "path.h"
+#include "prototypes.h"
+#include "sect.h"
+#include "xy.h"
+
+static int owned_and_navigable(char *, int, int, int);
+
+#define MAXROUTE	100
+#define valid(x,y)	((((x) ^ (y)) & 1) == 0)
+
+/*
+ * Ok, note that here we malloc some buffers.  BUT, we never
+ * free them.  Why, you may ask?  Because we want to allocate
+ * them based on world size which is now (or soon to be) dynamic,
+ * but we don't want to allocate each and every time, since that
+ * would be slow.  And, since world size only changes at init
+ * time, we can do this safely.
+ */
+static unsigned short *mapbuf;
+static unsigned short **mapindex;
+
+/*
+ * Find passable path from X, Y to EX, EY for nation OWN.
+ * BPATH is a buffer capable of holding at least MAXROUTE characters.
+ * If BIGMAP is null, all sectors are passable (useful for flying).
+ * Else it is taken to be a bmap.
+ * Sectors owned by or allied to OWN are then passable according to
+ * the usual rules.
+ * Other sectors are assumed to be passable when BIGMAP shows '.' or
+ * nothing.
+ * Return a path if found, else a null pointer.
+ * Wart: the path isn't terminated with 'h', except when if X,Y equals
+ * EX,EY.
+ */
+char *
+bestownedpath(char *bpath, char *bigmap,
+	      int x, int y, int ex, int ey, int own)
+{
+    int i, j, tx, ty, markedsectors;
+    int minx, maxx, miny, maxy, scanx, scany;
+    unsigned routelen;
+
+    if (!mapbuf)
+	mapbuf = malloc(WORLD_X * WORLD_Y * sizeof(*mapbuf));
+    if (!mapbuf)
+	return NULL;
+    if (!mapindex) {
+	mapindex = malloc(WORLD_X * sizeof(*mapindex));
+	if (mapindex) {
+	    /* Setup the map pointers */
+	    for (i = 0; i < WORLD_X; i++)
+		mapindex[i] = &mapbuf[WORLD_Y * i];
+	}
+    }
+    if (!mapindex)
+	return NULL;
+
+    x = XNORM(x);
+    y = YNORM(y);
+    ex = XNORM(ex);
+    ey = YNORM(ey);
+
+    if (x == ex && y == ey)
+	return "h";
+
+    if (!valid(x, y) || !valid(ex, ey))
+	return NULL;
+    if (!owned_and_navigable(bigmap, ex, ey, own))
+	return NULL;
+
+    for (i = 0; i < WORLD_X; i++)
+	for (j = 0; j < WORLD_Y; j++)
+	    mapindex[i][j] = 0xFFFF;	/* clear the workspace  */
+
+    routelen = 0;		/* path length is now 0 */
+    mapindex[x][y] = 0;		/* mark starting spot   */
+    minx = x - 2;		/* set X scan bounds    */
+    maxx = x + 2;
+    miny = y - 1;		/* set Y scan bounds    */
+    maxy = y + 1;
+
+    do {
+	if (++routelen == MAXROUTE)
+	    return NULL;
+	markedsectors = 0;
+	for (scanx = minx; scanx <= maxx; scanx++) {
+	    x = XNORM(scanx);
+	    for (scany = miny; scany <= maxy; scany++) {
+		y = YNORM(scany);
+		if (!valid(x, y))
+		    continue;
+		if (((mapindex[x][y] & 0x1FFF) == routelen - 1)) {
+		    for (i = DIR_FIRST; i <= DIR_LAST; i++) {
+			tx = x + diroff[i][0];
+			ty = y + diroff[i][1];
+			tx = XNORM(tx);
+			ty = YNORM(ty);
+			if (mapindex[tx][ty] == 0xFFFF) {
+			    if (owned_and_navigable(bigmap, tx, ty, own)) {
+				if (CANT_HAPPEN(i < DIR_FIRST || i > DIR_LAST))
+				    i = DIR_STOP;
+				mapindex[tx][ty] =
+				    ((i - DIR_FIRST + 1) << 13) + routelen;
+				markedsectors++;
+			    }
+			}
+			if (tx == ex && ty == ey) {
+			    bpath[routelen] = 0;
+			    while (routelen--) {
+				i = (mapindex[tx][ty] >> 13)
+				    - 1 + DIR_FIRST;
+				bpath[routelen] = dirch[i];
+				tx = tx - diroff[i][0];
+				ty = ty - diroff[i][1];
+				tx = XNORM(tx);
+				ty = YNORM(ty);
+			    }
+			    return bpath;
+			}
+		    }
+		}
+	    }
+	}
+	miny--;
+	maxy++;
+	minx -= 2;
+	maxx += 2;
+    } while (markedsectors);
+
+    return NULL;		/* no route possible    */
+}
+
+/*
+ * Return non-zero if sector X, Y is passable.
+ * If BIGMAP is null, all sectors are passable (useful for flying).
+ * Else it is taken to be a bmap.
+ * Sectors owned by or allied to OWN are checked according to the
+ * usual rules, and the result is correct.
+ * Other sectors are assumed to be passable when BIGMAP shows '.' or
+ * nothing.
+ */
+static int
+owned_and_navigable(char *bigmap, int x, int y, int own)
+{
+    char mapspot;
+    struct sctstr sect;
+
+    if (!bigmap)
+	return 1;
+
+    /* Owned or allied sector?  Check the real sector.  */
+    getsect(x, y, &sect);
+    if (sect.sct_own && relations_with(sect.sct_own, own) == ALLIED) {
+	/* FIXME duplicates shp_check_nav() logic */
+	switch (dchr[sect.sct_type].d_nav) {
+	case NAVOK:
+	    return 1;
+	case NAV_CANAL:
+	    /* FIXME return 1 when all ships have M_CANAL */
+	    return 0;
+	case NAV_02:
+	    return sect.sct_effic >= 2;
+	case NAV_60:
+	    return sect.sct_effic >= 60;
+	default:
+	    return 0;
+	}
+    }
+
+    /* Can only check bigmap */
+    mapspot = bigmap[sect.sct_uid];
+    return mapspot == '.' || mapspot == ' ' || mapspot == 0;
+}

src/lib/common/path.c

@@ -34,15 +34,45 @@
  *     Markus Armbruster, 2011
  */
 
+/*
+ * 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 <string.h>
+#include "../as/as.h"
 #include "file.h"
 #include "optlist.h"
 #include "path.h"
+#include "prototypes.h"
 #include "sect.h"
 #include "xy.h"
 
+#ifdef USE_PATH_FIND
+void
+bp_enable_cachepath(void)
+{
+}
+
+void
+bp_disable_cachepath(void)
+{
+}
+
+void
+bp_clear_cachepath(void)
+{
+}
+
 char *
 BestLandPath(char *path,
 	     struct sctstr *from,
@@ -112,3 +142,397 @@ BestAirPath(char *path, int fx, int fy, int tx, int ty)
 	strcpy(path, "h");
     return path;
 }
+#else	/* !USE_PATH_FIND */
+#define BP_ASHASHSIZE	128	/* A* queue hash table size */
+#define BP_NEIGHBORS	6	/* max number of neighbors */
+
+struct bestp {
+    int bp_mobtype;
+    struct as_data *adp;
+};
+
+static int bp_path(struct as_path *pp, char *buf);
+static int bp_neighbors(struct as_coord c, struct as_coord *cp, void *);
+static double bp_lbcost(struct as_coord from, struct as_coord to, void *);
+static double bp_realcost(struct as_coord from, struct as_coord to, void *);
+static double bp_seccost(struct as_coord from, struct as_coord to, void *);
+static int bp_coord_hash(struct as_coord c);
+
+/* We use this for caching neighbors.  It never changes except
+ * at reboot time (maybe) so we never need to free it */
+static struct sctstr **neighsects;
+
+static struct bestp *
+bp_init(void)
+{
+    struct bestp *bp;
+
+    bp = malloc(sizeof(*bp));
+    memset(bp, 0, sizeof(*bp));
+    bp->adp = as_init(BP_NEIGHBORS, BP_ASHASHSIZE, bp_coord_hash,
+		      bp_neighbors, bp_lbcost, bp_realcost,
+		      bp_seccost, bp);
+
+    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;
+}
+
+/*
+ * Find the best path from sector to to sector, and put the Empire movement
+ * string in path.  Return 0 on success, -1 on error.
+ * FIXME unsafe by design: assumes path[] has space; buffer overrun
+ * when path gets long!
+ */
+static int
+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;
+	adp->to.x = to->sct_x;
+	adp->to.y = to->sct_y;
+	mybestpath->bp_mobtype = mob_type;
+
+	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;
+    return 0;
+}
+
+/*
+ * Translate an A* path into an empire movement string.  Return 0 on
+ * success, -1 on failure.
+ */
+static int
+bp_path(struct as_path *pp, char *buf)
+{
+    struct as_path *np;
+    char *cp = buf;
+    int dx, dy;
+    int n;
+
+    np = pp->next;
+    while (np) {
+	dx = np->c.x - pp->c.x;
+	/* deal with wraparound from non-neg coords */
+	if (dx < -2)
+	    dx += WORLD_X;
+	else if (dx > 2)
+	    dx -= WORLD_X;
+	dy = np->c.y - pp->c.y;
+	if (dy < -1)
+	    dy += WORLD_Y;
+	else if (dy > 1)
+	    dy -= WORLD_Y;
+	for (n = 1; n <= 6; n++)
+	    if (dx == diroff[n][0] && dy == diroff[n][1])
+		break;
+	if (n > 6)
+	    return -1;
+
+	*cp++ = dirch[n];
+	pp = np;
+	np = np->next;
+    }
+    *cp = '\0';
+    return 0;
+}
+
+/*
+ * Find coords neighboring this sector; return number of such
+ * coords, and coordinartes themselves in an array pointed
+ * to by *cpp.
+ * XXX need to check ownership, sector types, etc.
+ */
+static int
+bp_neighbors(struct as_coord c, struct as_coord *cp, void *pp)
+{
+    struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
+    struct bestp *bp = pp;
+    coord x, y;
+    coord nx, ny;
+    int n = 0, i;
+    struct sctstr *sp, *from, **ssp;
+    /* Six pointers, just in case our cache isn't there */
+    struct sctstr *tsp[] = { NULL, NULL, NULL, NULL, NULL, NULL };
+    int sx, sy, offset;
+
+    x = c.x;
+    y = c.y;
+    sx = XNORM(x);
+    sy = YNORM(y);
+    offset = XYOFFSET(sx, sy);
+    from = &sectp[offset];
+
+    if (neighsects == NULL)
+	ssp = (struct sctstr **)&tsp[0];
+    else
+	ssp = (struct sctstr **)&neighsects[offset * 6];
+    for (i = 1; i <= 6; i++, ssp++) {
+	if (*ssp == NULL) {
+	    /* We haven't cached this neighbor yet */
+	    nx = x + diroff[i][0];
+	    ny = y + diroff[i][1];
+	    sx = XNORM(nx);
+	    sy = YNORM(ny);
+	    offset = XYOFFSET(sx, sy);
+	    sp = &sectp[offset];
+	    *ssp = sp;
+	} else {
+	    sp = *ssp;
+	    sx = sp->sct_x;
+	    sy = sp->sct_y;
+	}
+	/* No need to calculate cost each time, just make sure we can
+	   move through it.  We calculate it later. */
+	if (dchr[sp->sct_type].d_mob0 < 0)
+	    continue;
+	if (bp->bp_mobtype == MOB_RAIL && !SCT_HAS_RAIL(sp))
+	    continue;
+	if (sp->sct_own != from->sct_own)
+	    continue;
+	cp[n].x = sx;
+	cp[n].y = sy;
+	n++;
+    }
+    return n;
+}
+
+/*
+ * Compute a lower-bound on the cost from "from" to "to".
+ */
+/*ARGSUSED*/
+static double
+bp_lbcost(struct as_coord from, struct as_coord to, void *pp)
+{
+    struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
+    struct bestp *bp = pp;
+    int x, y, sx, sy, offset;
+
+    x = to.x;
+    y = to.y;
+    sx = XNORM(x);
+    sy = YNORM(y);
+    offset = XYOFFSET(sx, sy);
+    return sector_mcost(&sectp[offset], bp->bp_mobtype);
+}
+
+/*
+ * Compute the real cost to move from "from" to "to".
+ */
+static double
+bp_realcost(struct as_coord from, struct as_coord to, void *pp)
+{
+    return bp_lbcost(from, to, pp);
+}
+
+/*
+ * Tie breaker secondary metric (only used when lower bound costs
+ * are equal).
+ */
+/*ARGSUSED*/
+static double
+bp_seccost(struct as_coord from, struct as_coord to, void *pp)
+{
+    return mapdist((coord)from.x, (coord)from.y,
+		   (coord)to.x, (coord)to.y);
+}
+
+/*
+ * Hash a coordinate into an integer.
+ */
+static int
+bp_coord_hash(struct as_coord c)
+{
+    return ((abs(c.x) + 1) << 3) ^ abs(c.y);
+}
+
+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
+pathcost(struct sctstr *start, char *path, int mob_type)
+{
+    struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
+    unsigned i;
+    int o;
+    int cx, cy;
+    double cost = 0.0;
+    struct sctstr *sp;
+    int sx, sy, offset;
+
+    cx = start->sct_x;
+    cy = start->sct_y;
+
+    while (*path) {
+	if (*path == 'h') {
+	    path++;
+	    continue;
+	}
+	i = *path - 'a';
+	if (CANT_HAPPEN(i >= sizeof(dirindex) / sizeof(*dirindex)))
+	    break;
+	o = dirindex[i];
+	if (CANT_HAPPEN(o < 0))
+	    break;
+	cx += diroff[o][0];
+	cy += diroff[o][1];
+	sx = XNORM(cx);
+	sy = YNORM(cy);
+	offset = XYOFFSET(sx, sy);
+	sp = &sectp[offset];
+	cost += sector_mcost(sp, mob_type);
+	path++;
+    }
+
+    return cost;
+}
+
+char *
+BestDistPath(char *path,
+	     struct sctstr *from,
+	     struct sctstr *to, double *cost)
+{
+    return BestLandPath(path, from, to, cost, MOB_MOVE);
+}
+
+char *
+BestLandPath(char *path,
+	     struct sctstr *from,
+	     struct sctstr *to, double *cost, int mob_type)
+{
+    int length;
+
+    *path = 0;
+    *cost = 0.0;
+    if (best_path(from, to, path, mob_type) < 0)
+	return NULL;
+    *cost = pathcost(from, path, mob_type);
+    length = strlen(path);
+    path[length] = 'h';
+    path[length + 1] = '\0';
+    return path;
+}
+
+char *
+BestShipPath(char *path, int fx, int fy, int tx, int ty, int owner)
+{
+    char *map;
+
+    map = ef_ptr(EF_BMAP, owner);
+    if (!map)
+	return NULL;
+#ifdef TEST_PATH_FIND
+    double newc = path_find(fx, fy, tx, ty, owner, MOB_SAIL);
+    char *p = bestownedpath(path, map, fx, fy, tx, ty, owner);
+    double c;
+    size_t l;
+    char buf[MAX_PATH_LEN];
+
+    if (!p)
+	c = -1.0;
+    else {
+	l = strlen(p);
+	if (p[l-1] == 'h')
+	    l--;
+	c = l;
+    }
+
+    if (c != newc) {
+	path_find_route(buf, sizeof(buf), fx, fy, tx, ty);
+	printf("%d,%d -> %d,%d %d: old %g, new %g, %g off\n",
+	       fx, fy, tx, ty, MOB_FLY, c, newc, c - newc);
+	printf("\told: %s\n", p);
+	printf("\tnew: %s\n", buf);
+    }
+    return p;
+#else
+    return bestownedpath(path, map, fx, fy, tx, ty, owner);
+#endif
+}
+
+char *
+BestAirPath(char *path, int fx, int fy, int tx, int ty)
+{
+#ifdef TEST_PATH_FIND
+    double newc = path_find(fx, fy, tx, ty, 0, MOB_FLY);
+    char *p = bestownedpath(path, NULL, fx, fy, tx, ty, -1);
+    double c;
+    size_t l;
+    char buf[MAX_PATH_LEN];
+
+    if (!p)
+	c = -1.0;
+    else {
+	l = strlen(p);
+	if (p[l-1] == 'h')
+	    l--;
+	c = l;
+    }
+
+    if (c != newc) {
+	path_find_route(buf, sizeof(buf), fx, fy, tx, ty);
+	printf("%d,%d -> %d,%d %d: old %g, new %g, %g off\n",
+	       fx, fy, tx, ty, MOB_FLY, c, newc, c - newc);
+	printf("\told: %s\n", p);
+	printf("\tnew: %s\n", buf);
+    }
+    return p;
+#else
+    return bestownedpath(path, NULL, fx, fy, tx, ty, -1);
+#endif
+}
+#endif	/* !USE_PATH_FIND */

src/lib/common/pathfind.c

@@ -39,6 +39,7 @@
 #include "file.h"
 #include "nat.h"
 #include "optlist.h"
+#include "prototypes.h"
 #include "path.h"
 #include "sect.h"
 
@@ -51,8 +52,8 @@
 static char *bufrotate(char *buf, size_t bufsz, size_t i);
 
 /*
- * Dijkstra's algorithm.  Refer to your graph algorithm textbook for
- * how it works.  Implementation is specialized to hex maps.
+ * A* algorithm.  Refer to your graph algorithm textbook for how it
+ * works.  Implementation is specialized to hex maps.
  *
  * Define PATH_FIND_STATS for performance statistics on stdout.
  */
@@ -101,7 +102,7 @@ static struct pf_map *pf_map;
 struct pf_heap {
     int uid;			/* sector uid and */
     coord x, y;			/* coordinates, uid == XYOFFSET(x, y) */
-    double cost;		/* cost from source */
+    double f;			/* estimated cost from source to dest */
 };
 
 static int pf_nheap;		/* #entries in pf_nheap[] */
@@ -114,12 +115,13 @@ static coord pf_sx, pf_sy;
 static int pf_suid;
 static natid pf_actor;
 static double (*pf_sct_cost)(natid, int);
+static double (*pf_h)(coord, coord, coord, coord, double);
 
 /*
  * Performance statistics
  */
 #ifdef PATH_FIND_STATS
-static unsigned pf_nsearch, pf_nsource, pf_nopen, pf_nclose;
+static unsigned pf_nsearch, pf_nsource, pf_nopen, pf_nreopen, pf_nclose;
 static unsigned pf_nheap_max, pf_noway;
 static double pf_sumcost;
 #define STAT_INC(v) ((void)((v)++))
@@ -131,14 +133,12 @@ static double pf_sumcost;
 #define STAT_HIMARK(v, h) ((void)0)
 #endif	/* !PATH_FIND_STATS */
 
-#ifndef NDEBUG			/* silence "not used" warning */
 /* Is sector with uid UID open?  */
 static int
 pf_is_open(int uid)
 {
     return pf_map[uid].visit == pf_visit;
 }
-#endif
 
 /* Is sector with uid UID closed?  */
 static int
@@ -169,11 +169,11 @@ pf_check(void)
 	assert(0 <= uid && uid < WORLD_SZ());
 	assert(pf_map[uid].heapi == i);
 	assert(pf_map[uid].visit == pf_visit);
-	assert(pf_map[uid].cost <= pf_heap[i].cost);
+	assert(pf_map[uid].cost <= pf_heap[i].f);
 	c = 2 * i + 1;
-	assert(c >= pf_nheap || pf_heap[i].cost <= pf_heap[c].cost);
+	assert(c >= pf_nheap || pf_heap[i].f <= pf_heap[c].f);
 	c++;
-	assert(c >= pf_nheap || pf_heap[i].cost <= pf_heap[c].cost);
+	assert(c >= pf_nheap || pf_heap[i].f <= pf_heap[c].f);
     }
 
     for (uid = 0; uid < WORLD_SZ(); uid++) {
@@ -211,9 +211,9 @@ pf_sift_down(int n)
 
     assert(0 <= n && n < pf_nheap);
     for (r = n; (c = 2 * r + 1) < pf_nheap; r = c) {
-	if (c + 1 < pf_nheap && pf_heap[c].cost > pf_heap[c + 1].cost)
+	if (c + 1 < pf_nheap && pf_heap[c].f > pf_heap[c + 1].f)
 	    c++;
-	if (pf_heap[r].cost < pf_heap[c].cost)
+	if (pf_heap[r].f < pf_heap[c].f)
 	    break;
 	pf_heap_swap(r, c);
     }
@@ -227,7 +227,7 @@ pf_sift_up(int n)
 
     assert(0 <= n && n < pf_nheap);
     for (c = n; (p = (c - 1) / 2), c > 0; c = p) {
-	if (pf_heap[p].cost < pf_heap[c].cost)
+	if (pf_heap[p].f < pf_heap[c].f)
 	    break;
 	pf_heap_swap(p, c);
     }
@@ -237,25 +237,32 @@ pf_sift_up(int n)
  * Open the unvisited sector X,Y.
  * UID is sector uid, it equals XYOFFSET(X,Y).
  * Cheapest path from source comes from direction DIR and has cost COST.
+ * H is the estimated cost from X,Y to the destination.
  */
 static void
-pf_open(int uid, coord x, coord y, int dir, double cost)
+pf_open(int uid, coord x, coord y, int dir, double cost, double h)
 {
     int i;
 
-    STAT_INC(pf_nopen);
-    i = pf_nheap++;
-    STAT_HIMARK(pf_nheap_max, (unsigned)pf_nheap);
-    DPRINTF("pf: open %d,%d %g %c %d\n", x, y, cost, dirch[dir], i);
-    assert(pf_is_unvisited(uid));
-    pf_map[uid].visit = pf_visit;
+    if (pf_is_open(uid)) {
+	STAT_INC(pf_nreopen);
+	i = pf_map[uid].heapi;
+	DPRINTF("pf: reopen %d,%d %g %c %d\n", x, y, cost, dirch[dir], i);
+    } else {
+	assert(pf_is_unvisited(uid));
+	STAT_INC(pf_nopen);
+	i = pf_nheap++;
+	STAT_HIMARK(pf_nheap_max, (unsigned)pf_nheap);
+	DPRINTF("pf: open %d,%d %g %c %d\n", x, y, cost, dirch[dir], i);
+	pf_map[uid].heapi = i;
+	pf_map[uid].visit = pf_visit;
+	pf_heap[i].uid = uid;
+	pf_heap[i].x = x;
+	pf_heap[i].y = y;
+    }
     pf_map[uid].dir = dir;
-    pf_map[uid].heapi = i;
     pf_map[uid].cost = cost;
-    pf_heap[i].uid = uid;
-    pf_heap[i].x = x;
-    pf_heap[i].y = y;
-    pf_heap[i].cost = cost;
+    pf_heap[i].f = cost + h;
 
     pf_sift_up(i);
     pf_check();
@@ -285,7 +292,7 @@ pf_close(void)
 #ifdef PATH_FIND_DEBUG
 /*
  * Return cost from source to sector with uid UID.
- * It must be visited, i.e. open or closed.
+ * It must be open (cost is an estimate) or closed (cost is exact).
  */
 static double
 pf_cost(int uid)
@@ -337,9 +344,17 @@ rev_dir(int dir)
  * SX,SY is the source.
  * The cost to enter the sector with uid u is COST(ACTOR, u).
  * Negative value means the sector can't be entered.
+ * Optional H() is the heuristic: the cost from x,y to the destination
+ * dx,dy is at least H(x, y, dx, dy, c1d), where c1d is the cost to
+ * enter dx,dy.  The closer H() is to the true cost, the more
+ * efficient this function works.
+ * With a null H(), A* degenerates into Dijkstra's algorithm.  You can
+ * then call path_find_to() multiple times for the same source.  This
+ * is faster when you need many destinations.
  */
 static void
-pf_set_source(coord sx, coord sy, natid actor, double (*cost)(natid, int))
+pf_set_source(coord sx, coord sy, natid actor, double (*cost) (natid, int),
+	      double (*h) (coord, coord, coord, coord, double))
 {
     STAT_INC(pf_nsource);
     DPRINTF("pf: source %d,%d\n", sx, sy);
@@ -348,6 +363,7 @@ pf_set_source(coord sx, coord sy, natid actor, double (*cost)(natid, int))
     pf_suid = XYOFFSET(sx, sy);
     pf_actor = actor;
     pf_sct_cost = cost;
+    pf_h = h;
 
     if (!pf_map) {
 	pf_map = calloc(WORLD_SZ(), sizeof(*pf_map));
@@ -361,8 +377,6 @@ pf_set_source(coord sx, coord sy, natid actor, double (*cost)(natid, int))
 	pf_visit += 2;
 
     pf_nheap = 0;
-
-    pf_open(pf_suid, pf_sx, pf_sy, DIR_STOP, 0.0);
 }
 
 /*
@@ -373,7 +387,7 @@ path_find_to(coord dx, coord dy)
 {
     int duid;
     int uid, nuid, i;
-    double cost, c1;
+    double c1d, cost, c1;
     coord x, y, nx, ny;
 
     STAT_INC(pf_nsearch);
@@ -385,29 +399,38 @@ path_find_to(coord dx, coord dy)
 	return pf_map[duid].cost;
     }
 
+    c1d = pf_sct_cost(pf_actor, duid);
+    if (c1d < 0) {
+	DPRINTF("pf: done new %g\n", -1.0);
+	STAT_INC(pf_noway);
+	return -1;
+    }
+
+    if (pf_is_unvisited(pf_suid))
+	/* first search from this source */
+	pf_open(pf_suid, pf_sx, pf_sy, DIR_STOP, 0.0,
+		pf_h ? pf_h(pf_sx, pf_sy, dx, dy, c1d) : 0.0);
+    else
+	assert(!pf_h);		/* multiple searches only w/o heuristic */
+
     while (pf_nheap > 0 && (uid = pf_heap[0].uid) != duid) {
 	x = pf_heap[0].x;
 	y = pf_heap[0].y;
-	cost = pf_heap[0].cost;
 	pf_close();
+	cost = pf_map[uid].cost;
 
 	for (i = 0; i < 6; i++) { /* for all neighbors */
 	    nx = x_in_dir(x, DIR_FIRST + i);
 	    ny = y_in_dir(y, DIR_FIRST + i);
 	    nuid = XYOFFSET(nx, ny);
-	    /*
-	     * Cost to enter NX,NY doesn't depend on direction of
-	     * entry.  This X,Y is at least as expensive as any
-	     * previous one.  Therefore, cost to go to NX,NY via X,Y
-	     * is at least as high as any previously found route.
-	     * Skip neighbors that have a route already.
-	     */
-	    if (!pf_is_unvisited(nuid))
+	    if (pf_h ? pf_is_closed(nuid) : !pf_is_unvisited(nuid))
 		continue;
 	    c1 = pf_sct_cost(pf_actor, nuid);
 	    if (c1 < 0)
 		continue;
-	    pf_open(nuid, nx, ny, DIR_FIRST + i, cost + c1);
+	    if (pf_is_unvisited(nuid) || cost + c1 < pf_map[nuid].cost)
+		pf_open(nuid, nx, ny, DIR_FIRST + i, cost + c1,
+			pf_h ? pf_h(nx, ny, dx, dy, c1d) : 0);
 	}
     }
 
@@ -555,9 +578,10 @@ path_find_visualize(coord sx, coord sy, coord dx, coord dy)
 void
 path_find_print_stats(void)
 {
-    printf("pathfind %u searches, %u sources, %u opened, %u closed,"
+    printf("pathfind %u searches, %u sources,"
+	   " %u opened, %u reopened, %u closed,"
 	   " %u heap max, %zu bytes, %u noway, %g avg cost\n",
-	   pf_nsearch, pf_nsource, pf_nopen, pf_nclose,
+	   pf_nsearch, pf_nsource, pf_nopen, pf_nreopen, pf_nclose,
 	   pf_nheap_max,
 	   (WORLD_SZ() * (sizeof(*pf_map) + sizeof(*pf_heap))),
 	   pf_noway, pf_nsearch ? pf_sumcost / pf_nsearch : 0.0);
@@ -599,6 +623,20 @@ cost_rail(natid actor, int uid)
     return cost_land(actor, uid, MOB_RAIL);
 }
 
+static double
+h_move(coord x, coord y, coord dx, coord dy, double c1d)
+{
+    int md = mapdist(x, y, dx, dy);
+    return md ? c1d + (md - 1) * 0.001 : 0.0;
+}
+
+static double
+h_march_rail(coord x, coord y, coord dx, coord dy, double c1d)
+{
+    int md = mapdist(x, y, dx, dy);
+    return md ? c1d + (md - 1) * 0.02 : 0.0;
+}
+
 static double
 cost_sail(natid actor, int uid)
 {
@@ -634,10 +672,20 @@ cost_fly(natid actor, int uid)
     return 1.0;
 }
 
+static double
+h_sail_fly(coord x, coord y, coord dx, coord dy, double c1d)
+{
+    return mapdist(x, y, dx, dy);
+}
+
 static double (*cost_tab[])(natid, int) = {
     cost_move, cost_march, cost_rail, cost_sail, cost_fly
 };
 
+static double (*h[])(coord, coord, coord, coord, double) = {
+    h_move, h_march_rail, h_march_rail, h_sail_fly, h_sail_fly
+};
+
 /*
  * Start finding paths from SX,SY.
  * Use mobility costs for ACTOR and MOBTYPE.
@@ -645,7 +693,7 @@ static double (*cost_tab[])(natid, int) = {
 void
 path_find_from(coord sx, coord sy, natid actor, int mobtype)
 {
-    pf_set_source(sx, sy, actor, cost_tab[mobtype]);
+    pf_set_source(sx, sy, actor, cost_tab[mobtype], NULL);
 }
 
 /*
@@ -655,6 +703,6 @@ path_find_from(coord sx, coord sy, natid actor, int mobtype)
 double
 path_find(coord sx, coord sy, coord dx, coord dy, natid actor, int mobtype)
 {
-    pf_set_source(sx, sy, actor, cost_tab[mobtype]);
+    pf_set_source(sx, sy, actor, cost_tab[mobtype], h[mobtype]);
     return path_find_to(dx, dy);
 }

src/lib/update/finish.c

@@ -35,6 +35,8 @@
 
 #include <config.h>
 
+#include <assert.h>
+#include <math.h>
 #include <stdlib.h>
 #include <sys/resource.h>
 #include "distribute.h"
@@ -77,7 +79,19 @@ finish_sects(int etu)
 
     logerror("assembling paths...\n");
     getrusage(RUSAGE_SELF, &rus1);
+
+    /* First, enable the best_path cacheing */
+    bp_enable_cachepath();
+
+    /* Now assemble the paths */
     assemble_dist_paths(import_cost);
+
+    /* Now disable the best_path cacheing */
+    bp_disable_cachepath();
+
+    /* Now, clear the best_path cache that may have been created */
+    bp_clear_cachepath();
+
     getrusage(RUSAGE_SELF, &rus2);
     logerror("done assembling paths %g user %g system",
 	     rus2.ru_utime.tv_sec + rus2.ru_utime.tv_usec / 1e6
@@ -110,6 +124,7 @@ finish_sects(int etu)
 
 }
 
+#if (defined(USE_PATH_FIND) || defined(TEST_PATH_FIND)) && !defined(DIST_PATH_NO_REUSE)
 static int
 distcmp(const void *p, const void *q)
 {
@@ -126,6 +141,7 @@ distcmp(const void *p, const void *q)
 	return d;
     return b - a;
 }
+#endif
 
 static void
 assemble_dist_paths(double *import_cost)
@@ -133,10 +149,17 @@ assemble_dist_paths(double *import_cost)
     struct sctstr *sp;
     struct sctstr *dist;
     int n;
+#if defined(USE_PATH_FIND) || defined(TEST_PATH_FIND)
     static int *job;
     int uid, i;
     coord dx = 1, dy = 0;	/* invalid */
 
+#ifdef DIST_PATH_NO_REUSE
+    for (uid = 0; NULL != (sp = getsectid(uid)); uid++) {
+	import_cost[uid] = -1;
+	if (sp->sct_dist_x == sp->sct_x && sp->sct_dist_y == sp->sct_y)
+	    continue;
+#else
     if (!job)
 	job = malloc(WORLD_SZ() * sizeof(*job));
 
@@ -157,18 +180,75 @@ assemble_dist_paths(double *import_cost)
 
     for (i = 0; i < n; i++) {
 	uid = job[i];
+#endif	/* !DIST_PATH_NO_REUSE */
 	sp = getsectid(uid);
 	dist = getsectp(sp->sct_dist_x, sp->sct_dist_y);
 	if (CANT_HAPPEN(!dist))
 	    continue;
 	if (sp->sct_own != dist->sct_own)
 	    continue;
+#ifdef DIST_PATH_NO_REUSE
+#if DIST_PATH_NO_REUSE == 1
+	import_cost[uid] = path_find(sp->sct_dist_x, sp->sct_dist_y,
+				     sp->sct_x, sp->sct_y, dist->sct_own,
+				     MOB_MOVE);
+#else
+	path_find_from(sp->sct_dist_x, sp->sct_dist_y,
+		       dist->sct_own, MOB_MOVE);
+	import_cost[uid] = path_find_to(sp->sct_x, sp->sct_y);
+#endif
+#else
 	if (sp->sct_dist_x != dx || sp->sct_dist_y != dy) {
 	    dx = sp->sct_dist_x;
 	    dy = sp->sct_dist_y;
 	    path_find_from(dx, dy, dist->sct_own, MOB_MOVE);
 	}
 	import_cost[uid] = path_find_to(sp->sct_x, sp->sct_y);
+#endif
     }
+#endif	/* USE_PATH_FIND || TEST_PATH_FIND */
+#if !defined(USE_PATH_FIND) || defined(TEST_PATH_FIND)
+    char *path;
+    double d;
+    char buf[512];
+
+    for (n = 0; NULL != (sp = getsectid(n)); n++) {
+#ifdef TEST_PATH_FIND
+	double new_imc = import_cost[n];
+#endif
+	import_cost[n] = -1;
+	if ((sp->sct_dist_x == sp->sct_x) && (sp->sct_dist_y == sp->sct_y))
+	    continue;
+	dist = getsectp(sp->sct_dist_x, sp->sct_dist_y);
+	if (CANT_HAPPEN(!dist))
+	    continue;
+	if (sp->sct_own != dist->sct_own)
+	    continue;
+	/* Now, get the best distribution path over roads */
+	/* Note we go from the dist center to the sector.  This gives
+	   us the import path for that sector. */
+	path = BestDistPath(buf, dist, sp, &d);
+	if (path)
+	    import_cost[n] = d;
+#ifdef TEST_PATH_FIND
+	if (fabs(import_cost[n] - new_imc) >= 1e-6) {
+	    printf("%d,%d <- %d,%d %d: old %g, new %g, %g off\n",
+		   sp->sct_dist_x, sp->sct_dist_y,
+		   sp->sct_x, sp->sct_y, MOB_MOVE,
+		   import_cost[n], new_imc, import_cost[n] - new_imc);
+	    printf("\told: %s\n", path);
+	    d = path_find(sp->sct_dist_x, sp->sct_dist_y,
+			  sp->sct_x, sp->sct_y, dist->sct_own, MOB_MOVE);
+	    assert(d - new_imc < 1e-6);
+	    path_find_route(buf, sizeof(buf),
+			    sp->sct_dist_x, sp->sct_dist_y,
+			    sp->sct_x, sp->sct_y);
+	    printf("\tnew: %s\n", buf);
+	}
+#endif	/* TEST_PATH_FIND */
+    }
+#endif	/* !USE_PATH_FIND || TEST_PATH_FIND */
+#if defined(USE_PATH_FIND) || defined(TEST_PATH_FIND)
     path_find_print_stats();
+#endif
 }