URL:
<http://gna.org/bugs/?13218>
Summary: infinite loop in the AI if it persistently tries to
move unit to occupied square
Project: Battle for Wesnoth
Submitted by: crab
Submitted on: Thursday 03/19/2009 at 07:51
Category: Bug
Severity: 4 - Important
Priority: 5 - Normal
Item Group: Artificial Intelligence
Status: None
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Release: r33849
Operating System: Debian GNU/Linu
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Details:
How-to-reproduce:
start multiplayer\local game
use map 2p-Caves of the Basilisk,
options: Unlimited turns, village gold 2, exp mod 50%,
0=use map settings, 1=observers, 0=time limit
two players:
#1 (me): loyalists\lieutenant
#2 (default ai): drakes\drake flare
[or download attached save]
do nothing for two turns. Wesnoth hangs.
See the screenshot to understand what the AI tries to do - it tries to return
leader to nearest keep, but it is already occupied.
in ai::move_unit ( src/ai.cpp:704 ) , unit will not be moved if the
destination square is not empty (which is reasonable), and ai::move_unit
will return 'from' to tell that no move was done. but,
formula_ai::execute_variant (src/formula_ai.cpp:1904) ignores that return
value and instead checks 'is the destination square now occupied'. Therefore,
if the AI persistently tries to move unit from A to occupied B (in my case, AI
tried to return leader to the starting keep), it will get in a nice infinite
loop, since it is 'it doesn't make a move and yet returns true' situation.
--
the solution is two-fold.
Firstly, formula_ai::execute_variant (in src/formula_ai.cpp) must be modified
to check the return value of ai::move_unit (see the attached patch). Wesnoth
will not hang anymore, but the AI will sit still and try to repeat this move
each turn.
Secondly, the AI must be changed to avoid moves to occupied squares.
_______________________________________________________
File Attachments:
-------------------------------------------------------
Date: Thursday 03/19/2009 at 07:51 Name: formula_ai.patch Size: 1kB By:
crab
<http://gna.org/bugs/download.php?file_id=5453>
-------------------------------------------------------
Date: Thursday 03/19/2009 at 07:51 Name: bug1.gz Size: 28kB By: crab
<http://gna.org/bugs/download.php?file_id=5454>
_______________________________________________________
Reply to this item at:
<http://gna.org/bugs/?13218>
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