URL:
<http://gna.org/patch/?1144>
Summary: Incorrect handling of poison attack when suggesting
best attack in user interface
Project: Battle for Wesnoth
Submitted by: crab
Submitted on: Friday 03/27/2009 at 20:01
Priority: 3 - Low
Status: In Progress
Privacy: Public
Assigned to: crab
Originator Email:
Open/Closed: Open
Discussion Lock: Any
_______________________________________________________
Details:
1.
When assasin attack a goblin, the game thinks that his melee attack is
better that his ranged.
2.
This happens because of a bug in evaluation code - the presence of
poison on assasin's ranged attacks actually decreases chances to use it.
3.
4.
in GDB, in src/actions.cpp, just before returning from evaluation code
which compares assasin's ranged attack (A) and assasin's melee attack (B)
5.
===
6.
// Does combat A give us a better result than combat B?
7.
bool battle_context::better_combat(const combatant &us_a, const
combatant &them_a,
8.
const combatant &us_b, const combatant &them_b,
9.
double harm_weight)
10.
{
11.
double a, b;
12.
13.
// Compare: P(we kill them) - P(they kill us).
14.
a = them_a.hp_dist[0] - us_a.hp_dist[0] * harm_weight;
15.
b = them_b.hp_dist[0] - us_b.hp_dist[0] * harm_weight;
16.
if (a - b < -0.01)
17.
return false;
18.
if (a - b > 0.01)
19.
return true;
20.
21.
// Add poison to calculations
22.
double poison_a_us = (us_a.poisoned) *
game_config::poison_amount;
23.
double poison_a_them = (them_a.poisoned) *
game_config::poison_amount;
24.
double poison_b_us = (us_b.poisoned) *
game_config::poison_amount;
25.
double poison_b_them = (them_b.poisoned) *
game_config::poison_amount;
26.
// Compare: damage to them - damage to us (average_hp replaces
-damage)
27.
a = (us_a.average_hp()-poison_a_us)*harm_weight -
(them_a.average_hp()-poison_a_them);
28.
b = (us_b.average_hp()-poison_b_us)*harm_weight -
(them_b.average_hp()-poison_b_them);
29.
if (a - b < -0.01)
30.
return false;
31.
if (a - b > 0.01)
32.
return true;
33.
34.
// All else equal: go for most damage.
35.
return them_a.average_hp() < them_b.average_hp();
36.
}
37.
38.
===
39.
(gdb) print poison_b_them
40.
$17 = 0
41.
(gdb) print poison_a_us
42.
$18 = 0
43.
(gdb) print poison_a_them
44.
$19 = 7.4879999999999995
45.
(gdb) print poison_b_us
46.
$20 = 0
47.
(gdb) print poison_b_them
48.
$21 = 0
49.
(gdb) print a
50.
$22 = -8.6880000000000024
51.
(gdb) print b
52.
$23 = -6.3500000000000014
53.
54.
It is a sign error. That bonus of +7.4 (instead of -7.4 from the poison
turned "a" from a good attack with +13 to a bad attack with
"-8.6880000000000024"
55.
56.
Proposed patch:
57.
==========================================
58.
--- actions.cpp (revision 34146)
59.
+++ actions.cpp (working copy)
60.
-532,8 +532,8 @@
61.
double poison_b_us = (us_b.poisoned) *
game_config::poison_amount;
62.
double poison_b_them = (them_b.poisoned) *
game_config::poison_amount;
63.
// Compare: damage to them - damage to us (average_hp replaces
-damage)
64.
- a = (us_a.average_hp()+poison_a_us)*harm_weight -
(them_a.average_hp()+poison_a_them);
65.
- b = (us_b.average_hp()+poison_b_us)*harm_weight -
(them_b.average_hp()+poison_b_them);
66.
+ a = (us_a.average_hp()-poison_a_us)*harm_weight -
(them_a.average_hp()-poison_a_them);
67.
+ b = (us_b.average_hp()-poison_b_us)*harm_weight -
(them_b.average_hp()-poison_b_them);
68.
if (a - b < -0.01)
69.
return false;
70.
if (a - b > 0.01)
_______________________________________________________
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<http://gna.org/patch/?1144>
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