Attempted at making all things world gen thread proof.

Specifically, caching is tested thread proof.

src/main/java/ca/recrown/islandsurvivalcraft/Types/Point2.java

@@ -3,15 +3,13 @@ package ca.recrown.islandsurvivalcraft.Types;
 import java.util.Objects;
 
 public class Point2 {
-    public int x, y;
+    public final int x, y;
+    private final int hash;
 
     public Point2(int x, int y) {
         this.x = x;
         this.y = y;
-    }
+        this.hash = Objects.hash(x, y);
-
-    public Point2() {
-        this(0, 0);
     }
 
     @Override
@@ -23,8 +21,12 @@ public class Point2 {
         return false;
     }
 
+    public boolean fastEquals(Point2 point) {
+        return point.hashCode() == this.hash && x == point.x && y == point.y;
+    }
+
     @Override
     public int hashCode() {
-        return Objects.hash(x, y);
+        return hash;
     }
 }

src/main/java/ca/recrown/islandsurvivalcraft/caching/Cache.java

@@ -2,16 +2,19 @@ package ca.recrown.islandsurvivalcraft.caching;
 
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.locks.ReentrantLock;
 
 public class Cache<Key, Value> {
     private final int maxSize;
     private final ConcurrentHashMap<Key, CacheValue<Value>> data;
     private final ConcurrentLinkedQueue<Key> occurrenceOrder;
+    private ReentrantLock cleaningLock;
 
     public Cache(int maxSize) {
         data = new ConcurrentHashMap<>(maxSize);
         occurrenceOrder = new ConcurrentLinkedQueue<>();
         this.maxSize = maxSize;
+        cleaningLock = new ReentrantLock(true);
     }
 
     public Cache() {
@@ -19,18 +22,27 @@ public class Cache<Key, Value> {
     }
 
     public void setValue(Key key, Value value) {
-        data.put(key, new CacheValue<>(value));
+        CacheValue<Value> previous = data.get(key);
+        CacheValue<Value> fresh = new CacheValue<>(value);
+        if (previous != null) fresh.occurrence += previous.occurrence;
         occurrenceOrder.add(key);
+        data.put(key, fresh);
+
         if (data.size() > maxSize) {
             int occ = 0;
             do {
+                cleaningLock.lock();
+                try {
                     Key potentialKey = occurrenceOrder.poll();
                     CacheValue<Value> potential = data.get(potentialKey);
-                potential.decreaseOccurence();
+                    potential.occurrence--;
-                occ = potential.getOccurrence();
+                    occ = potential.occurrence;
                     if (occ < 1) {
                         data.remove(potentialKey);
                     } 
+                } finally {
+                    cleaningLock.unlock();
+                }
             } while (occ > 0);
         }
     }
@@ -43,12 +55,18 @@ public class Cache<Key, Value> {
      * @return the value associated to the key.
      */
     public Value getValue(Key key) {
-        CacheValue<Value> res = data.get(key);
+        CacheValue<Value> res = null;
+        cleaningLock.lock();
+        try {
+            res = data.get(key);
             if (res == null) return null;
-
+            res.occurrence++;
-        res.increaseOccurrence();
             occurrenceOrder.add(key);
-        return res.getValue();
+        } finally {
+            cleaningLock.unlock();
+        }
+
+        return res.data;
     }
 
     public void clearCache() {

src/main/java/ca/recrown/islandsurvivalcraft/caching/CacheValue.java

@@ -1,32 +1,10 @@
 package ca.recrown.islandsurvivalcraft.caching;
 
-public class CacheValue <ValueType> {
+class CacheValue<ValueType> {
-    private int occurrence = 1;
+    public volatile int occurrence = 1;
-    private final ValueType value;
+    public final ValueType data;
-
-    /**
-     * @return the occurrence
-     */
-    public int getOccurrence() {
-        return occurrence;
-    }
-
-    public void increaseOccurrence() {
-        occurrence++;
-    }
-
-    public void decreaseOccurence() {
-        occurrence--;
-    }
 
     public CacheValue(ValueType value) {
-        this.value = value;
+        this.data = value;
-    }
-
-    /**
-     * @return the value
-     */
-    public ValueType getValue() {
-        return value;
     }
 }

src/main/java/ca/recrown/islandsurvivalcraft/world/IslandWorldGeneratorAlternator.java

@@ -1,7 +1,8 @@
 package ca.recrown.islandsurvivalcraft.world;
 
-import java.util.HashMap;
 import java.util.Random;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.bukkit.World;
 
@@ -13,19 +14,19 @@ import ca.recrown.islandsurvivalcraft.world.generation.IslandWorldGenerator;
  * Uses IslandWorldGenerator as the container for each world.
  */
 public class IslandWorldGeneratorAlternator {
-    private HashMap<Long, IslandWorldGenerator> chunkGenerator;
+    private final ConcurrentHashMap<UUID, IslandWorldGenerator> chunkGenerators;
-    private IslandBiomeGenerator islandBiomeGenerator;
+    private final IslandBiomeGenerator islandBiomeGenerator;
 
     public IslandWorldGeneratorAlternator(IslandBiomeGenerator biomeGenerator) {
-        chunkGenerator = new HashMap<>();
+        this.chunkGenerators = new ConcurrentHashMap<>();
         this.islandBiomeGenerator = biomeGenerator;
     }
 
-    public synchronized IslandWorldGenerator getIslandChunkGeneratorSystem(World world, Random random) {
+    public IslandWorldGenerator getIslandChunkGeneratorSystem(World world, Random random) {
-        long tid = Thread.currentThread().getId();
+        UUID wUuid = world.getUID();
-        if (!chunkGenerator.containsKey(tid)) {
+        if (!chunkGenerators.containsKey(wUuid)) {
-            chunkGenerator.put(tid, new IslandWorldGenerator(world, islandBiomeGenerator.getInstance(), random));
+            chunkGenerators.put(wUuid, new IslandWorldGenerator(world, islandBiomeGenerator.getInstance(), random));
         }
-        return chunkGenerator.get(tid);
+        return chunkGenerators.get(wUuid);
     }
 }

src/main/java/ca/recrown/islandsurvivalcraft/world/IslandWorldMapper.java

@@ -10,9 +10,9 @@ import ca.recrown.islandsurvivalcraft.pathfinding.CoordinateValidatable;
 import ca.recrown.islandsurvivalcraft.pathfinding.DepthFirstSearch;
 
 public class IslandWorldMapper implements CoordinateValidatable {
-    private Cache<Point2, Double> blockValueCache;
+    private final Cache<Point2, Double> blockValueCache;
 
-    private SimplexOctaveGenerator noiseGenerator;
+    private final SimplexOctaveGenerator noiseGenerator;
     private final int noiseOctaves = 4;
     private final float islandBlockGenerationPercent = 16;
     private final float exaggerationFactor = 1.2f;
@@ -28,7 +28,7 @@ public class IslandWorldMapper implements CoordinateValidatable {
         dfs = new DepthFirstSearch(this);
         this.noiseGenerator = new SimplexOctaveGenerator(random, noiseOctaves);
         noiseGenerator.setScale(scale);
-        blockValueCache = new Cache<>(4096);
+        blockValueCache = new Cache<>(32768);
     }
     
     /**
@@ -113,6 +113,7 @@ public class IslandWorldMapper implements CoordinateValidatable {
      */
     public double getWorldBlockValue(int worldX, int worldZ) {
         Point2 p = new Point2(worldX, worldZ);
+
         Double res = blockValueCache.getValue(p);
         if (res == null) {
             double portionSea = 1f - (this.islandBlockGenerationPercent / 100f);

src/main/java/ca/recrown/islandsurvivalcraft/world/generation/BedrockGenerator.java

@@ -5,7 +5,7 @@ import java.util.Random;
 import org.bukkit.util.noise.SimplexOctaveGenerator;
 
 public class BedrockGenerator {
-    private SimplexOctaveGenerator noiseGenerator;
+    private final SimplexOctaveGenerator noiseGenerator;
     private final int maxBedrockHeight;
     private final int minBedrockHeight;
 

src/main/java/ca/recrown/islandsurvivalcraft/world/generation/BiomePerIslandGenerator.java

@@ -1,7 +1,5 @@
 package ca.recrown.islandsurvivalcraft.world.generation;
 
-import java.util.Arrays;
-
 import org.bukkit.World;
 import org.bukkit.block.Biome;
 
@@ -16,32 +14,31 @@ import ca.recrown.islandsurvivalcraft.world.IslandWorldMapper;
 
 //Note: technically, the validators have to be run on land, and so, some condition checks may not be nessecary.
 public class BiomePerIslandGenerator implements IslandBiomeGenerator {
-    private boolean initialized;
+    private volatile boolean initialized;
     private final TemperatureMapGenerator temperatureMapGenerator;
     private final Cache<Point2, Biome[][]> chunkBiomesCache;
     private final Cache<Point2, Boolean> chunkGenStatusCache;
-    private IslandWorldMapper worldIslandMap;
+    private volatile IslandWorldMapper worldIslandMap;
-    private BiomeSelector biomeSelector;
+    private volatile BiomeSelector biomeSelector;
-    private World world;
+    private volatile World world;
     private final DepthFirstSearch freshCachePropagator;
     private final DepthFirstSearch existenceChecker;
-    private FreshCachePropagationInfo freshCachePropInfo;
+    private final FreshCachePropagationInfo freshCachePropInfo;
-    private PreviousGenerationInfo existenceInfo;
+    private final PreviousGenerationInfo existenceInfo;
-    private Point2 currChunkCoords;
+    private volatile Point2 currChunkCoords;
-    private final Biome[][] localChunkCache;
+    private volatile Biome[][] localChunkCache;
     
     float temperature;
 
     public BiomePerIslandGenerator() {
         this.temperatureMapGenerator = new TemperatureMapGenerator();
-        chunkBiomesCache = new Cache<>(1024);
+        chunkBiomesCache = new Cache<>(512);
-        chunkGenStatusCache = new Cache<>(1024);
+        chunkGenStatusCache = new Cache<>(512);
         freshCachePropInfo = new FreshCachePropagationInfo();
         freshCachePropagator = new DepthFirstSearch(freshCachePropInfo);
         existenceInfo = new PreviousGenerationInfo();
         existenceChecker = new DepthFirstSearch(existenceInfo);
         localChunkCache = new Biome[16][16];
-        currChunkCoords = new Point2();
     }
     
     @Override
@@ -61,12 +58,9 @@ public class BiomePerIslandGenerator implements IslandBiomeGenerator {
 
     @Override
     public Biome GenerateBiome(int chunkX, int chunkZ, int localX, int localZ) {
-        if (chunkX != currChunkCoords.x || chunkZ != currChunkCoords.y) {
+        if (currChunkCoords == null || chunkX != currChunkCoords.x || chunkZ != currChunkCoords.y) {
-            currChunkCoords.x = chunkX;
+            currChunkCoords = new Point2(chunkX, chunkZ);
-            currChunkCoords.y = chunkZ;
+            localChunkCache = new Biome[16][16];
-            for (int i = 0; i < 16; i++) {
-                Arrays.fill(localChunkCache[i], null);
-            }
         }
         int worldX = Utilities.addMagnitude(16 * chunkX, localX);
         int worldZ = Utilities.addMagnitude(16 * chunkZ, localZ);
@@ -96,7 +90,7 @@ public class BiomePerIslandGenerator implements IslandBiomeGenerator {
         int localZ = Math.abs(worldZ % 16);
         Point2 chunkCoords = new Point2(worldX / 16, worldZ / 16);
 
-        if (chunkCoords.equals(this.currChunkCoords) && localChunkCache[localX][localZ] != null) {
+        if (chunkCoords.fastEquals(this.currChunkCoords) && localChunkCache[localX][localZ] != null) {
             return localChunkCache[localX][localZ];
         }
 
@@ -127,7 +121,7 @@ public class BiomePerIslandGenerator implements IslandBiomeGenerator {
         int localZ = Math.abs(worldZ % 16);
         Point2 chunkCoords = new Point2(worldX / 16, worldZ / 16);
 
-        if (chunkCoords.equals(this.currChunkCoords)) localChunkCache[localX][localZ] = biome;
+        if (chunkCoords.fastEquals(this.currChunkCoords)) localChunkCache[localX][localZ] = biome;
 
         Biome[][] chunkBiomes = chunkBiomesCache.getValue(chunkCoords);
         if (chunkBiomes == null) chunkBiomes = new Biome[16][16];
@@ -157,7 +151,7 @@ public class BiomePerIslandGenerator implements IslandBiomeGenerator {
         @Override
         public boolean validate(int x, int y) {
             Point2 chunkCoords = new Point2(x / 16, y / 16);
-            return chunkCoords.x == currChunkCoords.x && chunkCoords.y == currChunkCoords.y && worldIslandMap.isIsland(x, y);
+            return chunkCoords.fastEquals(currChunkCoords) && worldIslandMap.isIsland(x, y);
         }
 
         public boolean allBiomesAcquired() {

src/main/java/ca/recrown/islandsurvivalcraft/world/generation/IslandWorldGenerator.java

@@ -9,6 +9,7 @@ import org.bukkit.block.Biome;
 import org.bukkit.generator.ChunkGenerator.BiomeGrid;
 import org.bukkit.generator.ChunkGenerator.ChunkData;
 
+import ca.recrown.islandsurvivalcraft.Utilities;
 import ca.recrown.islandsurvivalcraft.world.BiomeSelector;
 import ca.recrown.islandsurvivalcraft.world.IslandWorldMapper;
 import ca.recrown.islandsurvivalcraft.world.shaders.WorldHeightShader;
@@ -44,8 +45,9 @@ public class IslandWorldGenerator {
     }
 
     public void GenerateChunk(int chunkX, int chunkZ, int localX, int localZ, ChunkData chunk, BiomeGrid biomeGrid) {
-        int worldX = 16 * chunkX + localX;
+        int worldX = Utilities.addMagnitude(16 * chunkX, localX);
-        int worldZ = 16 * chunkZ + localZ;
+        int worldZ = Utilities.addMagnitude(16 * chunkZ, localZ);
+        
         // gets the bedrock.
         int bedrockHeight = bedrockGenerator.getBedrockHeight(worldX, worldZ);
 

src/main/java/ca/recrown/islandsurvivalcraft/world/generation/TemperatureMapGenerator.java

@@ -12,7 +12,7 @@ class TemperatureMapGenerator {
     private final double frequency = 0.5D;
     private final double amplitude = 0.5D;
 
-    private SimplexOctaveGenerator noiseGenerator;
+    private volatile SimplexOctaveGenerator noiseGenerator;
 
     public TemperatureMapGenerator() {
         temperatureCache = new Cache<>(1024);

src/main/java/ca/recrown/islandsurvivalcraft/world/shaders/WorldHeightShader.java

@@ -9,12 +9,12 @@ import org.bukkit.util.noise.SimplexOctaveGenerator;
 import ca.recrown.islandsurvivalcraft.world.IslandWorldMapper;
 
 public class WorldHeightShader {
-    private Random random;
+    private final Random random;
-    private SimplexOctaveGenerator noiseGenerator;
+    private final SimplexOctaveGenerator noiseGenerator;
-    private IslandWorldMapper islandLocator;
+    private final IslandWorldMapper islandLocator;
-    private int seaLevel;
+    private final int seaLevel;
-    private int worldHeight;
+    private final int worldHeight;
-    private int minimumHeight;
+    private final int minimumHeight;
     private final float probabilityOfAdditive = 0.75f;
 
     public WorldHeightShader(long seed, IslandWorldMapper islandLocator, int seaLevel, int worldHeight, int minimumHeight) {