[Freeciv-Dev] Re: (PR#6123) Loop in ai_manage_airunit

["Gregory Berkolaiko" <Gregory.Berkolaiko@xxxxxxxxxxxx>]

On Wed, 10 Sep 2003, Gregory Berkolaiko wrote:

> I see where the problem is and I think I know what to do.
> 
> There are two parts of the problem, 
> 1. The attack rule change was not properly supported across the board.
> 2. There is no loop prevention in ai_manage_airunit.

Attached is a patch to ai_manage_airunit which makes it more robust and
prevent loops from happenning.  I haven't tested it yet, tomorrow.

G.

? ai_activities.diff
Index: ai/aiair.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/ai/aiair.c,v
retrieving revision 1.19
diff -u -r1.19 aiair.c
--- ai/aiair.c  2003/08/01 15:58:07     1.19
+++ ai/aiair.c  2003/09/10 23:31:27
@@ -36,7 +36,8 @@
 /**************************************************************************
  * Looks for nearest airbase for punit.
  * Returns 0 if not found.
- * TODO: Special handicaps for planes running out of fuel
+ * TODO: 1. Use proper refuel_iterate, like in ai_find_strategic_airbase
+ *       2. Special handicaps for planes running out of fuel
  *       IMO should be less restrictive than general H_MAP, H_FOG
  *************************************************************************/
 static bool find_nearest_airbase(int x, int y, struct unit *punit, 
@@ -278,8 +279,12 @@
  ***********************************************************************/
 void ai_manage_airunit(struct player *pplayer, struct unit *punit)
 {
-  enum goto_result result = GR_FAILED;
+  int dest_x = punit->x, dest_y = punit->y;
+  /* Loop prevention */
+  int moves = punit->moves_left;
+  int id = punit->id;
 
+
   CHECK_UNIT(punit);
 
   if (!is_airunit_refuel_point(punit->x, punit->y, 
@@ -296,14 +301,13 @@
                                 goto_dest_x(punit), goto_dest_y(punit),
                                 pplayer) >= 0) {
       /* It's an ok GOTO, just go there */
-      result = do_unit_goto(punit, GOTO_MOVE_ANY, FALSE);
+      ai_unit_gothere(punit);
     } else if (find_nearest_airbase(punit->x, punit->y, punit, 
                             &refuel_x, &refuel_y)) {
       /* Go refuelling */
       set_goto_dest(punit, refuel_x, refuel_y);
       freelog(LOG_DEBUG, "Sent %s to refuel", unit_type(punit)->name);
-      set_unit_activity(punit, ACTIVITY_GOTO);
-      result = do_unit_goto(punit, GOTO_MOVE_ANY, FALSE);
+      ai_unit_gothere(punit);
     } else {
       if (punit->fuel == 1) {
        freelog(LOG_DEBUG, "Oops, %s is fallin outta sky", 
@@ -311,59 +315,47 @@
       }
       return;
     }
-
-    /* Check if we got there okay */
-    if (result != GR_ARRIVED) {
-      freelog(LOG_DEBUG, "Something happened to our unit along the way");
-      /* TODO: some rescuing, but not running into dead-loop */
-    }
 
-  } else if (punit->fuel == unit_type(punit)->fuel
-            && find_something_to_bomb(punit, punit->x, punit->y) > 0) {
+  } else if (punit->fuel == unit_type(punit)->fuel) {
+    /* We only leave a refuel point when we are on full fuel */
 
-    /* Found target, coordinates are in punit's goto_dest.
-     * TODO: separate attacking into a function, check for the best 
-     * tile to attack from */
-    assert(is_goto_dest_set(punit));
-    set_unit_activity(punit, ACTIVITY_GOTO);
-    if (!ai_unit_gothere(punit)) {
-      return; /* died */
-    }
-    /* goto would be aborted: "Aborting GOTO for AI attack procedures"
-     * now actually need to attack */
-
-    /* We could use ai_military_findvictim here, but I don't trust it... */
-    set_unit_activity(punit, ACTIVITY_IDLE);
-    if (is_tiles_adjacent(punit->x, punit->y,
-                         goto_dest_x(punit), goto_dest_y(punit))) {
-      int id = punit->id;
-      (void) handle_unit_move_request(punit, goto_dest_x(punit),
-                                     goto_dest_y(punit), TRUE, FALSE);
-      if ((punit = find_unit_by_id(id)) != NULL && punit->moves_left > 0) {
-       /* Fly home now */
-       ai_manage_airunit(pplayer, punit);
+    if (find_something_to_bomb(punit, punit->x, punit->y) > 0) {
+      /* Found target, coordinates are in punit's goto_dest.
+       * TODO: separate attacking into a function, check for the best 
+       * tile to attack from */
+      assert(is_goto_dest_set(punit));
+      if (!ai_unit_gothere(punit)) {
+        return; /* died */
       }
-    } else {
-      /* Ooops.  Now better come back home */
-      ai_manage_airunit(pplayer, punit);
-    }
 
-  } else {
-    int dest_x= punit->x, dest_y = punit->y;
-    
-    if (ai_find_strategic_airbase(punit, &dest_x, &dest_y)) {
+      /* goto would be aborted: "Aborting GOTO for AI attack procedures"
+       * now actually need to attack */
+      /* We could use ai_military_findvictim here, but I don't trust it... */
+      set_unit_activity(punit, ACTIVITY_IDLE);
+      if (is_tiles_adjacent(punit->x, punit->y,
+                            goto_dest_x(punit), goto_dest_y(punit))) {
+        (void) handle_unit_move_request(punit, goto_dest_x(punit),
+                                        goto_dest_y(punit), TRUE, FALSE);
+      }
+    } else if (ai_find_strategic_airbase(punit, &dest_x, &dest_y)) {
       freelog(LOG_DEBUG, "%s will fly to (%i, %i) (%s) to fight there",
               unit_type(punit)->name, dest_x, dest_y, 
               (map_get_city(dest_x, dest_y) ? 
                map_get_city(dest_x, dest_y)->name : ""));
       set_goto_dest(punit, dest_x, dest_y);
-      set_unit_activity(punit, ACTIVITY_GOTO);
-      result = do_unit_goto(punit, GOTO_MOVE_ANY, FALSE);
+      ai_unit_gothere(punit);
     } else {
       freelog(LOG_DEBUG, "%s cannot find anything to kill and is staying put", 
               unit_type(punit)->name);
       set_unit_activity(punit, ACTIVITY_IDLE);
     }
+  }
+
+  if ((punit = find_unit_by_id(id)) != NULL && punit->moves_left > 0
+      && punit->moves_left != moves) {
+    /* We have moved this turn, might have ended up stuck out in the fields
+     * so, as a safety measure, let's manage again */
+    ai_manage_airunit(pplayer, punit);
   }
 
 }