[freeciv-ai] Re: [Freeciv-Dev] (PR#9866) S1_14: AI fixes

["Per I. Mathisen" <per@xxxxxxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=9866 >

On Sun, 29 Aug 2004, Gregory Berkolaiko wrote:
> Your latest patch in the "fun Ai game" thread does much better job: it
> retains the check for whether we got assigned to the city and it compares
> with defense rather than 0.
>
> So I suggest we use it to fix S-branch.

Ok, here is the latest patch for cvs head, as I commit it. Changes since
last version is a check that we don't accidentially make an allied city to
our homecity, and assert in ai_unit_make_homecity() that this is not
attempted by other code. And some extra comments.

  - Per

Index: ai/aitools.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/ai/aitools.c,v
retrieving revision 1.120
diff -u -r1.120 aitools.c
--- ai/aitools.c        27 Aug 2004 17:36:52 -0000      1.120
+++ ai/aitools.c        31 Aug 2004 15:29:16 -0000
@@ -399,6 +399,8 @@
 bool ai_unit_make_homecity(struct unit *punit, struct city *pcity)
 {
   CHECK_UNIT(punit);
+  assert(punit->owner == pcity->owner);
+
   if (punit->homecity == 0 && !unit_has_role(punit->type, L_EXPLORER)) {
     /* This unit doesn't pay any upkeep while it doesn't have a homecity,
      * so it would be stupid to give it one. There can also be good reasons
Index: ai/aiunit.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/ai/aiunit.c,v
retrieving revision 1.330
diff -u -r1.330 aiunit.c
--- ai/aiunit.c 29 Aug 2004 20:14:41 -0000      1.330
+++ ai/aiunit.c 31 Aug 2004 15:29:16 -0000
@@ -328,7 +328,7 @@
 
 /**************************************************************************
   Return whether we should stay and defend a square, usually a city. Will
-  protect allied cities temporarily.
+  protect allied cities temporarily in case of grave danger.
 
   FIXME: We should check for fortresses here.
 **************************************************************************/
@@ -336,30 +336,40 @@
 {
   struct city *pcity = map_get_city(punit->x, punit->y);
   bool has_defense = FALSE;
-
-  CHECK_UNIT(punit);
+  int mydef;
+  int units = -2; /* WAG for grave danger threshold, seems to work */
 
   if (!pcity) {
     return FALSE;
   }
+  mydef = assess_defense_unit(pcity, punit, FALSE);
 
   unit_list_iterate(map_get_tile(pcity->x, pcity->y)->units, pdef) {
-    if (assess_defense_unit(pcity, punit, FALSE) >= 0
+    if (assess_defense_unit(pcity, pdef, FALSE) >= mydef
        && pdef != punit
        && pdef->homecity == pcity->id) {
       has_defense = TRUE;
     }
+    units++;
   } unit_list_iterate_end;
  
   /* Guess I better stay / you can live at home now */
-  if (!has_defense && pcity->ai.danger > 0) {
-    /* change homecity to this city */
+  if (!has_defense && pcity->ai.danger > 0 && punit->owner == pcity->owner) {
+    /* Change homecity to this city */
     if (ai_unit_make_homecity(punit, pcity)) {
       /* Very important, or will not stay -- Syela */
       ai_unit_new_role(punit, AIUNIT_DEFEND_HOME, pcity->x, pcity->y);
       return TRUE;
-    }
+    } /* else city cannot upkeep us! */
   }
+
+  /* Treat grave danger anyway if danger is over threshold, which is the
+   * number of units currently in the city. */
+  if (pcity->ai.grave_danger > units) {
+    ai_unit_new_role(punit, AIUNIT_DEFEND_HOME, pcity->x, pcity->y);
+    return TRUE;
+  }
+
   return FALSE;
 }