[Freeciv-Dev] [Fwd: Re: (PR#18222) [Patch] AI builds caravans]

[Marko Lindqvist <cazfi74@xxxxxxxxx>]

 It seems that RT never sent this to the list.


  After testing a lot of different versions, I think this works best
overall. I'll put this version in to more excessive testing. I plan to
commit this in a couple of days.


  - ML

diff -Nurd -X.diff_ignore freeciv/ai/advdomestic.c freeciv/ai/advdomestic.c
--- freeciv/ai/advdomestic.c    2006-07-06 22:00:04.765625000 +0300
+++ freeciv/ai/advdomestic.c    2006-07-07 15:08:51.546875000 +0300
@@ -130,6 +130,104 @@
   }
 }
 
+/***************************************************************************
+ * Evaluate the need for units (like caravans) that create trade routes.
+ * If pplayer is not advanced enough to build caravans, the corresponding
+ * tech will be stimulated.
+ ***************************************************************************/
+static void ai_choose_trade_route(struct city *pcity,
+                                 struct ai_choice *choice,
+                                  struct ai_data *ai)
+{
+  struct player *pplayer = city_owner(pcity);
+  struct unit_type *unit_type;
+  int want;
+  int income, bonus;
+  int trade_routes;
+  Continent_id continent = tile_get_continent(pcity->tile);
+  bool dest_city_found = FALSE;
+
+  if (city_list_size(pplayer->cities) < 5) {
+    /* Consider trade routes only if enough destination cities.
+     * This is just a quick check. We make more detailed check below. */
+    return;
+  }
+
+  if (num_role_units(F_TRADE_ROUTE) == 0) {
+    /* No such units available in the ruleset */
+    return;
+  }
+
+  /* Look for proper destination city at the same continent. */
+  city_list_iterate(pplayer->cities, acity) {
+    if (can_cities_trade(pcity, acity) && tile_get_continent(acity->tile) == 
continent) {
+      dest_city_found = TRUE;
+      break;
+    }
+  } city_list_iterate_end;
+
+  if(!dest_city_found) {
+    /* No proper destination city at the same continent. */
+    return;
+  }
+
+  unit_type = best_role_unit(pcity, F_TRADE_ROUTE);
+
+  if (!unit_type) {
+    /* We cannot build such units yet
+     * but we will consider it to stimulate science */
+    unit_type = get_role_unit(F_TRADE_ROUTE, 0);
+  }
+
+  trade_routes = city_num_trade_routes(pcity);
+
+  /* We consider only initial benefit from establishing trade route.
+   * We may actually get only initial benefit if both cities already
+   * have four trade routes, or if there already is route between them. */
+
+  /* We assume that we are creating trade route to city with 75% of
+   * pcitys trade 10 squares away. */
+  income = (10 + 10) * (1.75 * pcity->surplus[O_TRADE]) / 24 * 3;
+  bonus = get_city_bonus(pcity, EFT_TRADE_REVENUE_BONUS);
+  income = (float)income * pow(2.0, (double)bonus / 1000.0);
+
+  want = income * ai->gold_priority + income * ai->science_priority;
+
+  /* We get this income only once after all.
+   * This value is adjusted for most interesting gameplay.
+   * For optimal performance AI should build more caravans, but
+   * we want it to build less valued buildings too. */
+  want /= 130;
+
+  if (trade_routes == 0) {
+    /* If we have no trade routes at all, we are certainly creating a new one. 
*/
+    want += 20;
+  } else if (trade_routes < NUM_TRADEROUTES) {
+    /* Possibly creating a new traderoute */
+    want += 5;
+  }
+
+  want -= unit_build_shield_cost(unit_type) * SHIELD_WEIGHTING / 150;
+
+  CITY_LOG(LOG_DEBUG, pcity,
+           "want for trade route unit is %d (expected initial income %d)",
+           want, income);
+
+  if (want > choice->want) {
+    /* This sets our tech want in cases where we cannot actually build
+     * the unit. */
+    unit_type = ai_wants_role_unit(pplayer, pcity, F_TRADE_ROUTE, want);
+    if (unit_type != NULL) {
+      choice->want = want;
+      choice->type = CT_NONMIL;
+      choice->choice = unit_type->index;
+    } else {
+      CITY_LOG(LOG_DEBUG, pcity,
+               "would but could not build trade route unit, bumped reqs");
+    }
+  }
+}
+
 /************************************************************************** 
   This function should fill the supplied choice structure.
 
@@ -224,9 +322,14 @@
     copy_if_better_choice(&cur, choice);
 
     init_choice(&cur);
-    /* Consider city improvments */
+    /* Consider city improvements */
     ai_advisor_choose_building(pcity, &cur);
     copy_if_better_choice(&cur, choice);
+
+    init_choice(&cur);
+    /* Consider building caravan-type units for trade route */
+    ai_choose_trade_route(pcity, &cur, ai);
+    copy_if_better_choice(&cur, choice);
   }
 
   if (choice->want >= 200) {