Actually seed the random number generator used in the simulation. Reviewed by sanderd17, fixes #4127.

This was SVN commit r18604.

binaries/data/mods/public/gui/gamesetup/gamesetup.js

@@ -1282,11 +1282,9 @@ function launchGame()
 			g_GameAttributes.settings.PlayerData[player.player - 1].Name = player.name;
 	}
 
-	// This seed is only used for map-generation
+	// Seed used for both map generation and simulation
-	if (g_GameAttributes.mapType == "random")
+	g_GameAttributes.settings.Seed = Math.floor(Math.random() * Math.pow(2, 32));
-		g_GameAttributes.settings.Seed = Math.floor(Math.random() * 65536);
+	g_GameAttributes.settings.AISeed = Math.floor(Math.random() * Math.pow(2, 32));
-
-	g_GameAttributes.settings.AISeed = Math.floor(Math.random() * 65536);
 
 	// Used for identifying rated game reports for the lobby
 	g_GameAttributes.matchID = Engine.GetMatchID();

source/simulation2/Simulation2.cpp

@@ -752,6 +752,12 @@ void CSimulation2::SetMapSettings(const std::string& settings)
 void CSimulation2::SetMapSettings(JS::HandleValue settings)
 {
 	m->m_MapSettings = settings;
+
+	u32 seed = 0;
+	if (!m->m_ComponentManager.GetScriptInterface().GetProperty(m->m_MapSettings, "Seed", seed))
+		LOGWARNING("CSimulation2::SetInitAttributes: No seed value specified - using %d", seed);
+
+	m->m_ComponentManager.SetRNGSeed(seed);
 }
 
 std::string CSimulation2::GetMapSettingsString()

source/simulation2/Simulation2.h

@@ -108,12 +108,14 @@ public:
 	/**
 	 * Set the initial map settings (as a UTF-8-encoded JSON string),
 	 * which will be used to set up the simulation state.
+	 * Called from atlas.
 	 */
 	void SetMapSettings(const std::string& settings);
 
 	/**
 	 * Set the initial map settings, which will be used
 	 * to set up the simulation state.
+	 * Called from MapReader (for all map-types).
 	 */
 	void SetMapSettings(JS::HandleValue settings);
 

source/simulation2/system/ComponentManager.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -61,8 +61,6 @@ CComponentManager::CComponentManager(CSimContext& context, shared_ptr<ScriptRunt
 	context.SetComponentManager(this);
 
 	m_ScriptInterface.SetCallbackData(static_cast<void*> (this));
-
-	// TODO: ought to seed the RNG (in a network-synchronised way) before we use it
 	m_ScriptInterface.ReplaceNondeterministicRNG(m_RNG);
 	m_ScriptInterface.LoadGlobalScripts();
 
@@ -540,6 +538,11 @@ void CComponentManager::ResetState()
 	m_NextLocalEntityId = FIRST_LOCAL_ENTITY;
 }
 
+void CComponentManager::SetRNGSeed(u32 seed)
+{
+	m_RNG.seed(seed);
+}
+
 void CComponentManager::RegisterComponentType(InterfaceId iid, ComponentTypeId cid, AllocFunc alloc, DeallocFunc dealloc,
 		const char* name, const std::string& schema)
 {

source/simulation2/system/ComponentManager.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -295,6 +295,11 @@ public:
 	 */
 	void ResetState();
 
+	/**
+	 * Initializes the random number generator with a seed determined by the host.
+	 */
+	void SetRNGSeed(u32 seed);
+
 	// Various state serialization functions:
 	bool ComputeStateHash(std::string& outHash, bool quick);
 	bool DumpDebugState(std::ostream& stream, bool includeDebugInfo);

source/simulation2/tests/test_ComponentManager.h

@@ -96,6 +96,32 @@ public:
 		TS_ASSERT_EQUALS(man.AllocateNewLocalEntity(), (u32)FIRST_LOCAL_ENTITY);
 	}
 
+	void test_rng()
+	{
+		// Ensure we get the same random number with the same seed
+		double first;
+		{
+			CSimContext context;
+			CComponentManager man(context, g_ScriptRuntime);
+			man.SetRNGSeed(123);
+
+			if (!man.m_ScriptInterface.MathRandom(first))
+				TS_FAIL("Couldn't get random number!");
+		}
+
+		double second;
+		{
+			CSimContext context;
+			CComponentManager man(context, g_ScriptRuntime);
+			man.SetRNGSeed(123);
+
+			if (!man.m_ScriptInterface.MathRandom(second))
+				TS_FAIL("Couldn't get random number!");
+		}
+
+		TS_ASSERT_EQUALS(first, second);
+	}
+
 	void test_AddComponent_errors()
 	{
 		CSimContext context;