Put the Monte Carlo mode behind an advanced preference and update changelog

changelog

@@ -49,6 +49,15 @@ Version 1.13.4+dev:
      loggers activated in the gui print just like loggers activated in the 
      command line (i.e. messages appear in the console)
    * Fix bug #24762: Editor actions are out of sync after resizing.
+ * Performance:
+   * Added an advanced preference (Preferences -> Advanced ->
+     Allow damage calculation with Monte Carlo simulation) that, when enabled,
+     allows the damage calculation to operate by simulating a few thousand fights
+     instead of calculating exact probabilities of each outcome (when a heuristic
+     determines that it's probably faster). This method is inexact, but in very
+     complex battles (extremely high HP, drain, slow, berserk, etc.) it's
+     significantly faster than the default damage calculation method, and may be
+     necessary for acceptable performance.
  * WML engine:
    * Add color= attribute to [message].
    * Add [else], search_recall_list=, auto_recall= to [role]

data/advanced_preferences.cfg

@@ -188,6 +188,14 @@
     type=custom
 [/advanced_preference]
 
+[advanced_preference]
+    field=damage_prediction_allow_monte_carlo_simulation
+    name= _ "Allow damage calculation with Monte Carlo simulation"
+    description= _ "Allow the damage calculation window to simulate fights instead of using exact probability calculations"
+    type=boolean
+    default=no
+[/advanced_preference]
+
 #ifdef __UNUSED__
 [advanced_preference]
     field=joystick_support_enabled

players_changelog

@@ -32,6 +32,16 @@ Version 1.13.4+dev:
    * Added "Registered users only" checkbox to multiplayer configuration dialog which 
      when checked, only allows registered users to join the game
 
+ * Performance:
+   * Added an advanced preference (Preferences -> Advanced ->
+     Allow damage calculation with Monte Carlo simulation) that, when enabled,
+     allows the damage calculation to operate by simulating a few thousand fights
+     instead of calculating exact probabilities of each outcome (when a heuristic
+     determines that it's probably faster). This method is inexact, but in very
+     complex battles (extremely high HP, drain, slow, berserk, etc.) it's
+     significantly faster than the default damage calculation method, and may be
+     necessary for acceptable performance.
+
 Version 1.13.4:
  * Language and i18n:
    * Updated translations: British English, Russian.

src/attack_prediction.cpp

@@ -40,6 +40,7 @@
 
 #include "actions/attack.hpp"
 #include "game_config.hpp"
+#include "preferences.hpp"
 #include "random_new.hpp"
 #include <array>
 #include <cmath>
@@ -1986,7 +1987,8 @@ void combatant::fight(combatant &opp, bool levelup_considered)
 	const std::vector<combat_slice> opp_split = split_summary(opp.u_, opp.summary);
 
 	if (fight_complexity(split.size(), opp_split.size(), u_, opp.u_) >
-		MONTE_CARLO_SIMULATION_THRESHOLD)
+		MONTE_CARLO_SIMULATION_THRESHOLD &&
+		preferences::damage_prediction_allow_monte_carlo_simulation())
 	{
 		// A very complex fight. Use Monte Carlo simulation instead of exact
 		// probability calculations.

src/preferences.cpp

@@ -1041,5 +1041,15 @@ void set_disable_loadingscreen_animation(bool value)
 	set("disable_loadingscreen_animation", value);
 }
 
+bool damage_prediction_allow_monte_carlo_simulation()
+{
+	return get("damage_prediction_allow_monte_carlo_simulation", false);
+}
+
+void set_damage_prediction_allow_monte_carlo_simulation(bool value)
+{
+	set("damage_prediction_allow_monte_carlo_simulation", value);
+}
+
 } // end namespace preferences
 

src/preferences.hpp

@@ -263,6 +263,9 @@ namespace preferences {
 	bool disable_loadingscreen_animation();
 	void set_disable_loadingscreen_animation(bool value);
 
+	bool damage_prediction_allow_monte_carlo_simulation();
+	void set_damage_prediction_allow_monte_carlo_simulation(bool value);
+
 } // end namespace preferences
 
 #endif