[Freeciv-Dev] (PR#13277) air units, fuel, and pathfinding (PF) / goto

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=13277 >

> [jdorje - Thu Jun 16 20:06:32 2005]:
> 
> Currently PF doesn't handle fuel.  It handles air units but assumes that
> fuel == 1 for all units, so all non-airbase positions are dangerous.
> Basically this means that bombers aren't as efficient as they should be.
> 
> This can be fixed.  However it won't be especially easy.  There's
> probably already a ticket for it actually, but I sure can't find it.
> 
> I believe the best suggestion so far is to fake it.  Basically if you
> have a unit with fuel F1, and move rate M1 you transform it into a new
> unit with fuel 1 and move rate M2=F1*M1.  Now you get the optimal path
> using the same algorithm as before (that works with fuel 1) but certain
> characteristics of the path are wrong.  For instance the turns and MP
> for each position on the path are incorrect, so you have to do a reverse
> of the transformation at the end to provide the correct values in each
node.

Here is a preliminary patch to do this.  Air is supported in the core
pathfinding code by a move_turns parameter (which for air units is equal
to the amount of fuel).  The caller is expected to adjust the move_rate
and moves_left_initially by this value included in the pf_parameter). 
The core PF code then adjusts the returned positions based on this value
so that the correct number of turns and moves left are given back.

It's a little buggy however.  It won't work with waypoints since the
start_moves_left isn't carried over properly.  Also for some reason the
number of turns isn't being shown properly.

I think the solution to all this is to move the fuel entirely into the
core PF.

- The pf_parameter gets a fuel_left_initially.  move_turns is renamed
simply as fuel.
- Multiplication of the turns is done internally in path_finding.c.
- Then the client/goto.c code will also have to know about fuel,
tracking the units of fuel available at the start and end of each path
(just like moves left is already tracked).

-jason

Index: data/default/units.ruleset
===================================================================
RCS file: /home/freeciv/CVS/freeciv/data/default/units.ruleset,v
retrieving revision 1.68
diff -u -r1.68 units.ruleset
--- data/default/units.ruleset  2 May 2005 08:45:21 -0000       1.68
+++ data/default/units.ruleset  17 Jun 2005 21:49:02 -0000
@@ -966,7 +966,7 @@
 [unit_fighter]
 name          = _("Fighter")
 move_type     = "Air"
-tech_req      = "Flight"
+tech_req      = "None"
 obsolete_by   = "Stealth Fighter"
 graphic       = "u.fighter"
 graphic_alt   = "-"
@@ -974,7 +974,7 @@
 sound_move_alt = "m_generic"
 sound_fight   = "f_fighter"
 sound_fight_alt = "f_generic"
-build_cost    = 60
+build_cost    = 1
 pop_cost      = 0
 attack        = 4
 defense       = 3
@@ -994,7 +994,7 @@
 [unit_bomber]
 name          = _("Bomber")
 move_type     = "Air"
-tech_req      = "Advanced Flight"
+tech_req      = "None"
 obsolete_by   = "Stealth Bomber"
 graphic       = "u.bomber"
 graphic_alt   = "-"
@@ -1002,16 +1002,16 @@
 sound_move_alt = "m_generic"
 sound_fight   = "f_bomber"
 sound_fight_alt = "f_generic"
-build_cost    = 120
+build_cost    = 1
 pop_cost      = 0
 attack        = 12
 defense       = 1
 hitpoints     = 20
 firepower     = 2
-move_rate     = 8
+move_rate     = 2
 vision_range  = 2
 transport_cap = 0
-fuel          = 2
+fuel          = 8
 uk_happy      = 1
 uk_shield     = 1
 uk_food       = 0
@@ -1064,7 +1064,7 @@
 sound_move_alt = "m_generic"
 sound_fight   = "f_stealth_fighter"
 sound_fight_alt = "f_generic"
-build_cost    = 80
+build_cost    = 1
 pop_cost      = 0
 attack        = 8
 defense       = 4

Index: common/aicore/path_finding.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/common/aicore/path_finding.c,v
retrieving revision 1.31
diff -u -r1.31 path_finding.c
--- common/aicore/path_finding.c        2 May 2005 15:42:53 -0000       1.31
+++ common/aicore/path_finding.c        17 Jun 2005 21:56:32 -0000
@@ -535,8 +535,14 @@
     + pf_map->params->moves_left_initially;
   if (pf_map->params->turn_mode == TM_BEST_TIME ||
       pf_map->params->turn_mode == TM_WORST_TIME) {
+    int base_mr = pf_map->params->move_rate / pf_map->params->move_turns;
+
     pos->turn = get_turn(pf_map, node->cost);
     pos->moves_left = get_moves_left(pf_map, node->cost);
+
+    pos->turn *= pf_map->params->move_turns;
+    pos->turn += pos->moves_left / base_mr;
+    pos->moves_left %= base_mr;
   } else if (pf_map->params->turn_mode == TM_NONE ||
             pf_map->params->turn_mode == TM_CAPPED) {
     pos->turn = -1;
Index: common/aicore/path_finding.h
===================================================================
RCS file: /home/freeciv/CVS/freeciv/common/aicore/path_finding.h,v
retrieving revision 1.11
diff -u -r1.11 path_finding.h
--- common/aicore/path_finding.h        10 Jan 2005 03:24:16 -0000      1.11
+++ common/aicore/path_finding.h        17 Jun 2005 21:56:32 -0000
@@ -296,6 +296,8 @@
   struct tile *start_tile;     /* Initial position */
   int moves_left_initially;
   int move_rate;               /* Move rate of the virtual unit */
+  int move_turns;               /* How many turns should be considered as
+                                * one (equal to fuel for air units). */
 
   struct player *owner;
 
Index: common/aicore/pf_tools.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/common/aicore/pf_tools.c,v
retrieving revision 1.32
diff -u -r1.32 pf_tools.c
--- common/aicore/pf_tools.c    23 Apr 2005 17:40:28 -0000      1.32
+++ common/aicore/pf_tools.c    17 Jun 2005 21:56:32 -0000
@@ -771,6 +771,8 @@
 static void pft_fill_unit_default_parameter(struct pf_parameter *parameter,
                                            struct unit *punit)
 {
+  int mr = unit_move_rate(punit);
+
   parameter->turn_mode = TM_CAPPED;
   parameter->get_TB = NULL;
   parameter->get_EC = NULL;
@@ -781,7 +783,16 @@
 
   parameter->start_tile = punit->tile;
   parameter->moves_left_initially = punit->moves_left;
-  parameter->move_rate = unit_move_rate(punit);
+  if (is_air_unit(punit)) {
+    if (punit->fuel > 1) {
+      parameter->moves_left_initially += mr * (punit->fuel - 1);
+    }
+    parameter->move_turns = unit_type(punit)->fuel;
+    parameter->move_rate = mr * parameter->move_turns;
+  } else {
+    parameter->move_rate = mr;
+    parameter->move_turns = 1;
+  }
   parameter->owner = unit_owner(punit);
   parameter->unit_flags = unit_type(punit)->flags;
 
Index: client/goto.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/client/goto.c,v
retrieving revision 1.86
diff -u -r1.86 goto.c
--- client/goto.c       28 May 2005 21:24:00 -0000      1.86
+++ client/goto.c       17 Jun 2005 21:56:33 -0000
@@ -248,7 +248,7 @@
     struct unit *punit = find_unit_by_id(goto_map.unit_id);
 
     p->start_tile = punit->tile;
-    p->start_moves_left = punit->moves_left;
+    p->start_moves_left = parameter.moves_left_initially;
   } else {
     struct part *prev = &goto_map.parts[goto_map.num_parts - 2];
 
@@ -260,7 +260,6 @@
   p->end_tile = p->start_tile;
   p->time = 0;
   parameter.start_tile = p->start_tile;
-  parameter.moves_left_initially = p->start_moves_left;
   p->map = pf_create_map(&parameter);
 }