? explore.txt
? data/mono
? data/mono.tilespec
? data/oldciv
? data/oldciv.tilespec
? data/oldciv_shields.tilespec
? data/tinydent
? data/tinydent.tilespec
Index: ai/aiunit.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/ai/aiunit.c,v
retrieving revision 1.229
diff -u -3 -p -r1.229 aiunit.c
--- ai/aiunit.c	2002/11/14 09:14:50	1.229
+++ ai/aiunit.c	2002/11/14 19:56:02
@@ -256,6 +256,71 @@ static bool tile_is_accessible(struct un
 }
  
 /**************************************************************************
+  Determine if a tile is likely to be water, given information that
+  the player actually has. Return the certainty that it's water
+  (0x80 = certain, 0x40 = no idea, 0 = certainly not).
+**************************************************************************/
+int likely_ocean(int x, int y, struct player *pplayer)
+{
+  int sum = 0;
+
+  if(map_get_known(x,y,pplayer))
+    {
+      /* we've seen the tile already. */
+      if(map_get_terrain(x,y) == T_OCEAN)
+	return 128;
+      else
+	return 0;
+    }
+  
+  /* without the bounds checks we get segfaults */
+  if(((x-1 >= 0) && map_get_known(x-1,y,pplayer) && 
+      map_get_terrain(x-1,y) == T_OCEAN) ||
+     ((x+1 < map.xsize) && map_get_known(x+1,y,pplayer) && 
+      map_get_terrain(x+1,y) == T_OCEAN) ||
+     ((y-1 >= 0) && map_get_known(x,y-1,pplayer) && 
+      map_get_terrain(x,y-1) == T_OCEAN) ||
+     ((y+1 < map.ysize) && map_get_known(x,y+1,pplayer) && 
+      (map_get_terrain(x,y+1) == T_OCEAN)))
+    {
+      /* we can tell by the border if there's land there. */
+      if(map_get_terrain(x,y) == T_OCEAN)
+	return 0x80;
+      else
+	return 0;
+    }
+
+  sum = 0x40;
+  /* average the adjacent 8 tiles */
+  square_iterate(x, y, 1, x1, y1) {
+    if((y1<0) || (y1>map.ysize))
+      continue;
+
+    if(map_get_known(x1,y1, pplayer))
+      {
+	/* this nearby tile is water */
+
+	if((x != x1) && (y != y1))
+	  {
+	    /* diagonals count for less. */
+	    if(map_get_terrain(x1,y1) == T_OCEAN)
+	      sum += 2;
+	    else
+	      sum -= 2;
+	  }
+	else
+	  {
+	    if(map_get_terrain(x1,y1) == T_OCEAN)
+	      sum += 4;
+	    else
+	      sum -= 4;
+	  }
+      }
+  } square_iterate_end;
+  return sum;
+}
+
+/**************************************************************************
 Handle eXplore mode of a unit (explorers are always in eXplore mode for AI) -
 explores unknown territory, finds huts.
 
@@ -378,21 +443,69 @@ bool ai_manage_explorer(struct unit *pun
   while (punit->moves_left > 0) {
     /* Best (highest) number of unknown tiles adjacent (in vision range) */
     int most_unknown = 0;
+
+    /* most desirable tile, given adjacent water */
+    int most_desirable = 0;
+
+    /* relative value of exploring ocean and land */
+    int landscore = 5;
+    int oceanscore = 60;
+
+    /* relative value of staying near known ocean and land */
+    int klandscore = 2;
+    int koceanscore = 25;
+
     /* Desired destination */
     int best_x = -1, best_y = -1;
 
+    if(is_sailing_unit(punit))
+      {
+	/* for sailing explorer, reverse desirable tiles */
+	int temp;
+
+	temp = landscore;
+	landscore = oceanscore;
+	oceanscore = temp;
+
+	temp = klandscore;
+	klandscore = koceanscore;
+	koceanscore = temp;
+      }
+
     /* Evaluate all adjacent tiles. */
     
     square_iterate(x, y, 1, x1, y1) {
       /* Number of unknown tiles in vision range around this tile */
       int unknown = 0;
       
+      int desirable = 0;
+      int ocean = 0;
+
       square_iterate(x1, y1, range, x2, y2) {
+	ocean = likely_ocean(x2,y2, pplayer);
         if (!map_get_known(x2, y2, pplayer))
-          unknown++;
+	  {
+	    unknown++;
+	    /* if it's a tile we don't know, weight the value of
+	     * exploring it by if it's likely to be ocean or not. 
+	     */
+	    if(ocean > 0x40)
+	      desirable += oceanscore;
+	    else if(ocean < 0x40)
+	      desirable += landscore;
+	  }
+	else
+	  {
+	    if(ocean > 0x40)
+	      desirable += koceanscore;
+	    else if(ocean < 0x40)
+	      desirable += klandscore;
+	  }
       } square_iterate_end;
 
-      if (unknown > most_unknown) {
+      /* regardless how desirable a tile is, if we don't discover
+       * any new territory, don't go there. */
+      if (unknown && (desirable > most_desirable)) {
         if (unit_flag(punit, F_TRIREME)
             && trireme_loss_pct(pplayer, x1, y1) != 0)
           continue;
@@ -414,7 +527,10 @@ bool ai_manage_explorer(struct unit *pun
         if (is_barbarian(pplayer) && map_has_special(x1, y1, S_HUT))
           continue;
           
+	if(unknown > most_unknown)
+	  most_unknown = unknown;
         most_unknown = unknown;
+	most_desirable = desirable;
         best_x = x1;
         best_y = y1;
       }
@@ -444,7 +560,7 @@ bool ai_manage_explorer(struct unit *pun
 
       if (broken) { break; } /* a move failed, so danger of endless loop */
     } else {
-      /* Everything is already explored. */
+      /* Everything is already explored. */ 
       break;
     }
   }