Added a cHeiGenCache object for caching generated heightmaps. World generation is now about twice as fast as before Rev 535 :)

git-svn-id: http://mc-server.googlecode.com/svn/trunk@538 0a769ca7-a7f5-676a-18bf-c427514a06d6

source/HeiGen.cpp

@@ -25,6 +25,96 @@ void cHeiGenFlat::GenHeightMap(int a_ChunkX, int a_ChunkZ, cChunkDef::HeightMap
 
 
 
+///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// cHeiGenCache:
+
+cHeiGenCache::cHeiGenCache(cTerrainHeightGen * a_HeiGenToCache, int a_CacheSize) :
+	m_HeiGenToCache(a_HeiGenToCache),
+	m_CacheSize(a_CacheSize),
+	m_CacheOrder(new int[a_CacheSize]),
+	m_CacheData(new sCacheData[a_CacheSize]),
+	m_NumHits(0),
+	m_NumMisses(0),
+	m_TotalChain(0)
+{
+	for (int i = 0; i < m_CacheSize; i++)
+	{
+		m_CacheOrder[i] = i;
+		m_CacheData[i].m_ChunkX = 0x7fffffff;
+		m_CacheData[i].m_ChunkZ = 0x7fffffff;
+	}
+}
+
+
+
+
+
+cHeiGenCache::~cHeiGenCache()
+{
+	delete m_CacheData;
+	delete m_CacheOrder;
+	delete m_HeiGenToCache;
+}
+
+
+
+
+
+void cHeiGenCache::GenHeightMap(int a_ChunkX, int a_ChunkZ, cChunkDef::HeightMap & a_HeightMap)
+{
+	if (((m_NumHits + m_NumMisses) % 1024) == 10)
+	{
+		LOGD("HeiGenCache: %d hits, %d misses, saved %.2f %%", m_NumHits, m_NumMisses, 100.0 * m_NumHits / (m_NumHits + m_NumMisses));
+		LOGD("HeiGenCache: Avg cache chain length: %.2f", (float)m_TotalChain / m_NumHits);
+	}
+	
+	for (int i = 0; i < m_CacheSize; i++)
+	{
+		if (
+			(m_CacheData[m_CacheOrder[i]].m_ChunkX != a_ChunkX) ||
+			(m_CacheData[m_CacheOrder[i]].m_ChunkZ != a_ChunkZ)
+		)
+		{
+			continue;
+		}
+		// Found it in the cache
+		int Idx = m_CacheOrder[i];
+		
+		// Move to front:
+		for (int j = i; j > 0; j--)
+		{
+			m_CacheOrder[j] = m_CacheOrder[j - 1];
+		}
+		m_CacheOrder[0] = Idx;
+		
+		// Use the cached data:
+		memcpy(a_HeightMap, m_CacheData[Idx].m_HeightMap, sizeof(a_HeightMap));
+		
+		m_NumHits++;
+		m_TotalChain += i;
+		return;
+	}  // for i - cache
+	
+	// Not in the cache:
+	m_NumMisses++;
+	m_HeiGenToCache->GenHeightMap(a_ChunkX, a_ChunkZ, a_HeightMap);
+	
+	// Insert it as the first item in the MRU order:
+	int Idx = m_CacheOrder[m_CacheSize - 1];
+	for (int i = m_CacheSize - 1; i > 0; i--)
+	{
+		m_CacheOrder[i] = m_CacheOrder[i - 1];
+	}  // for i - m_CacheOrder[]
+	m_CacheOrder[0] = Idx;
+	memcpy(m_CacheData[Idx].m_HeightMap, a_HeightMap, sizeof(a_HeightMap));
+	m_CacheData[Idx].m_ChunkX = a_ChunkX;
+	m_CacheData[Idx].m_ChunkZ = a_ChunkZ;
+}
+
+
+
+
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 // cHeiGenClassic:
 

source/HeiGen.h

@@ -39,6 +39,42 @@ protected:
 
 
 
+/// A simple cache that stores N most recently generated chunks' heightmaps; N being settable upon creation
+class cHeiGenCache :
+	public cTerrainHeightGen
+{
+public:
+	cHeiGenCache(cTerrainHeightGen * a_HeiGenToCache, int a_CacheSize);  // Takes ownership of a_HeiGenToCache
+	~cHeiGenCache();
+	
+protected:
+
+	cTerrainHeightGen * m_HeiGenToCache;
+	
+	struct sCacheData
+	{
+		int m_ChunkX;
+		int m_ChunkZ;
+		cChunkDef::HeightMap m_HeightMap;
+	} ;
+	
+	// To avoid moving large amounts of data for the MRU behavior, we MRU-ize indices to an array of the actual data
+	int          m_CacheSize;
+	int *        m_CacheOrder;  // MRU-ized order, indices into m_CacheData array
+	sCacheData * m_CacheData;   // m_CacheData[m_CacheOrder[0]] is the most recently used
+	
+	// Cache statistics
+	int m_NumHits;
+	int m_NumMisses;
+	int m_TotalChain;  // Number of cache items walked to get to a hit (only added for hits)
+	
+	virtual void GenHeightMap(int a_ChunkX, int a_ChunkZ, cChunkDef::HeightMap & a_HeightMap) override;
+} ;
+
+
+
+
+
 class cHeiGenClassic :
 	public cTerrainHeightGen
 {

source/cChunkGenerator.cpp

@@ -177,10 +177,12 @@ void cChunkGenerator::InitHeightGen(cIniFile & a_IniFile)
 		HeightGenName = "classic";
 	}
 	
+	bool CacheOffByDefault = false;
 	if (NoCaseCompare(HeightGenName, "flat") == 0)
 	{
 		int Height = a_IniFile.GetValueI("Generator", "FlatHeight", 5);
 		m_HeightGen = new cHeiGenFlat(Height);
+		CacheOffByDefault = true;  // We're generating faster than a cache would retrieve data
 	}
 	else if (NoCaseCompare(HeightGenName, "classic") == 0)
 	{
@@ -201,6 +203,21 @@ void cChunkGenerator::InitHeightGen(cIniFile & a_IniFile)
 		}
 		m_HeightGen = new cHeiGenBiomal(m_Seed, *m_BiomeGen);
 	}
+	
+	// Add a cache, if requested:
+	int CacheSize = a_IniFile.GetValueI("Generator", "HeightGenCacheSize", CacheOffByDefault ? 0 : 64);
+	if (CacheSize > 0)
+	{
+		if (CacheSize < 4)
+		{
+			LOGWARNING("Heightgen cache size set too low, would hurt performance instead of helping. Increasing from %d to %d", 
+				CacheSize, 4
+			);
+			CacheSize = 4;
+		}
+		LOGINFO("Using a cache for Heightgen of size %d.", CacheSize);
+		m_HeightGen = new cHeiGenCache(m_HeightGen, CacheSize);
+	}
 }