<URL: http://bugs.freeciv.org/Ticket/Display.html?id=39852 >
Daniel Markstedt wrote:
> I'm generally for freedom. If the player wants to goto their stealth
> fighter to certain death, the gui should allow them to do it. It's not
> uncommon to make suicide attacks with air units anyway. Let's leave
> this behavior as it is.
>
...
> The issue here is that the pathfinding code believes this goto can be
> completed, while the poor stealth fighter in fact only gets halfway
> and crashes. It must somehow believe the air unit will become refuled
> just because a friendly city is nearby. This is IMHO in the scope of
> this ticket.
>
These are incompatible goals. Here's the coding compromise:
* for AI, allow 1/2 round trip only when starting at fueling base.
* for user, allow up to 1/2 the remaining fuel, no matter where we're
starting. This allows a user to set waypoints to control the path. But
at the final step, they won't necessarily be able to land.
int have = get_moves_left_initially(param);
if (have >= moves * 2
&& (is_possible_base_fuel(param->start_tile, param)
|| !param->owner->ai.control)) {
/* has enough fuel for round trip. */
return FALSE;
}
Found an existing static function for determining remaining moves in
path_finding.c -- made it accessible. There are (at least) 3 different
ways being used to calculate this; perhaps this narrows down the solution.
> Certainly not for 2.1. It would be a useful feature if city-hopping
> could be done automagically, but as you say it can be done with
> waypoints.
>
Found airgoto.c make_list_of_refuel_points() -- it just doesn't seem to
be used (or work) consistently.
(heavy sigh)
Anyway, I just checked this in to S2_1, and will handle the other branches
only after verification....
Committed S2_1 revision 13944.
Index: common/aicore/path_finding.h
===================================================================
--- common/aicore/path_finding.h (revision 13943)
+++ common/aicore/path_finding.h (working copy)
@@ -397,7 +397,7 @@
/* The map itself. Opaque type. */
struct pf_map;
-/* ==================== Functions =================================== */
+/* ==================== Map/Path Functions ========================== */
/* Returns a map which can be used to query for paths or to iterate
* over all paths. Does not perform any computations itself, just sets
@@ -449,4 +449,8 @@
/* Return the current parameters for the given map. */
struct pf_parameter *pf_get_parameter(struct pf_map *map);
+/* ==================== Parameter Functions ========================= */
+
+int get_moves_left_initially(const struct pf_parameter *param);
+
#endif
Index: common/aicore/pf_tools.c
===================================================================
--- common/aicore/pf_tools.c (revision 13943)
+++ common/aicore/pf_tools.c (working copy)
@@ -529,7 +529,19 @@
&& (terrain_has_flag(ptile->terrain, TER_UNSAFE)
|| (is_ocean(ptile->terrain) && !is_safe_ocean(ptile))));
}
+
/****************************************************************************
+ Refueling base for air units.
+****************************************************************************/
+static bool is_possible_base_fuel(const struct tile *ptile,
+ struct pf_parameter *param)
+{
+ /* All airbases are considered possible, simply attack enemies. */
+ return (is_allied_city_tile(ptile, param->owner)
+ || tile_has_special(ptile, S_AIRBASE));
+}
+
+/****************************************************************************
Position-dangerous callback for air units.
****************************************************************************/
static bool is_pos_dangerous_fuel(const struct tile *ptile,
@@ -537,29 +549,30 @@
struct pf_parameter *param)
{
int moves = SINGLE_MOVE * real_map_distance(param->start_tile, ptile);
- int fuel = param->move_rate * param->fuel_left_initially;
+ int have = get_moves_left_initially(param);
- if (fuel < moves) {
+ if (have < moves) {
/* not enough fuel. */
return TRUE;
}
- if (fuel >= moves * 2) {
+ if (have >= moves * 2
+ && (is_possible_base_fuel(param->start_tile, param)
+ || !param->owner->ai.control)) {
/* has enough fuel for round trip. */
return FALSE;
}
- if (fuel >= moves
- && (is_allied_city_tile(ptile, param->owner)
- || tile_has_special(ptile, S_AIRBASE))) {
- /* All airbases are considered non-dangerous, although non-allied ones
- * are inaccessible. */
+ if (TILE_UNKNOWN != known
+ && (is_possible_base_fuel(ptile, param)
+ || is_enemy_city_tile(ptile, param->owner))) {
+ /* allow attacks, even suicidal ones */
return FALSE;
}
- if (is_enemy_unit_tile(ptile, param->owner)
- || is_enemy_city_tile(ptile, param->owner)) {
- /* allow attacks, even suicidal ones */
+ if (TILE_KNOWN == known
+ && is_enemy_unit_tile(ptile, param->owner)) {
+ /* don't reveal unknown units */
return FALSE;
}
Index: common/aicore/path_finding.c
===================================================================
--- common/aicore/path_finding.c (revision 13943)
+++ common/aicore/path_finding.c (working copy)
@@ -121,7 +121,7 @@
turn. Thus the rest of the PF code doesn't actually know that the unit
has fuel, it just thinks it has that many more MP.
****************************************************************************/
-static int get_moves_left_initially(const struct pf_parameter *param)
+int get_moves_left_initially(const struct pf_parameter *param)
{
return (param->moves_left_initially
+ (param->fuel_left_initially - 1) * param->move_rate);
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