Paper/Spigot-Server-Patches/0455-Optimise-entity-hard-collision-checking.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Wed, 15 Apr 2020 18:08:53 -0700
Subject: [PATCH] Optimise entity hard collision checking

Very few entities actually hard collide, so store them in their own
entity slices and provide a special getEntites type call just for them.
This reduces entity collision checking impact (in my testing) by 25%
for crammed entities (shove 130 cows into an 8x6 area in one chunk).
Less crammed entities are likely to show significantly less benefit.
Effectively, this patch optimises crammed entity situations.

diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
index cb24f27bc443880b18ffc36236f6ec7174c9d493..b65ae2d6919a67498d0646c5522735086fec00c1 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -91,6 +91,54 @@ public class Chunk implements IChunkAccess {
     private final int[] inventoryEntityCounts = new int[16];
     // Paper end
 
+    // Paper start - optimise hard collision handling
+    final com.destroystokyo.paper.util.maplist.EntityList[] hardCollidingEntities = new com.destroystokyo.paper.util.maplist.EntityList[16];
+
+    {
+        for (int i = 0, len = this.hardCollidingEntities.length; i < len; ++i) {
+            this.hardCollidingEntities[i] = new com.destroystokyo.paper.util.maplist.EntityList();
+        }
+    }
+
+    public final void getHardCollidingEntities(@Nullable Entity entity, AxisAlignedBB axisalignedbb, List<Entity> into, Predicate<Entity> predicate) {
+        // copied from getEntities
+        int min = MathHelper.floor((axisalignedbb.minY - 2.0D) / 16.0D);
+        int max = MathHelper.floor((axisalignedbb.maxY + 2.0D) / 16.0D);
+
+        min = MathHelper.clamp(min, 0, this.hardCollidingEntities.length - 1);
+        max = MathHelper.clamp(max, 0, this.hardCollidingEntities.length - 1);
+
+        for (int k = min; k <= max; ++k) {
+            com.destroystokyo.paper.util.maplist.EntityList entityList = this.hardCollidingEntities[k];
+            Entity[] entities = entityList.getRawData();
+
+            for (int i = 0, len = entityList.size(); i < len; ++i) {
+                Entity entity1 = entities[i];
+                if (entity1.shouldBeRemoved) continue; // Paper
+
+                if (entity1 != entity && entity1.getBoundingBox().intersects(axisalignedbb) && (predicate == null || predicate.test(entity1))) {
+                    into.add(entity1);
+
+                    if (!(entity1 instanceof EntityEnderDragon)) {
+                        continue;
+                    }
+
+                    EntityComplexPart[] aentitycomplexpart = ((EntityEnderDragon) entity1).getComplexParts();
+                    int l = aentitycomplexpart.length;
+
+                    for (int i1 = 0; i1 < l; ++i1) {
+                        EntityComplexPart entitycomplexpart = aentitycomplexpart[i1];
+
+                        if (entitycomplexpart != entity && entitycomplexpart.getBoundingBox().intersects(axisalignedbb) && (predicate == null || predicate.test(entitycomplexpart))) {
+                            into.add(entitycomplexpart);
+                        }
+                    }
+                }
+            }
+        }
+    }
+    // Paper end - optimise hard collision handling
+
     public Chunk(World world, ChunkCoordIntPair chunkcoordintpair, BiomeStorage biomestorage, ChunkConverter chunkconverter, TickList<Block> ticklist, TickList<FluidType> ticklist1, long i, @Nullable ChunkSection[] achunksection, @Nullable Consumer<Chunk> consumer) {
         this.sections = new ChunkSection[16];
         this.e = Maps.newHashMap();
@@ -546,7 +594,7 @@ public class Chunk implements IChunkAccess {
         entity.chunkY = k;
         entity.chunkZ = this.loc.z;
         this.entities.add(entity); // Paper - per chunk entity list
-        this.entitySlices[k].add(entity);
+        this.entitySlices[k].add(entity); if (entity.hardCollides()) this.hardCollidingEntities[k].add(entity); // Paper - optimise hard colliding entities
         // Paper start
         if (entity instanceof EntityItem) {
             itemCounts[k]++;
@@ -583,7 +631,7 @@ public class Chunk implements IChunkAccess {
             entity.entitySlice = null;
             entity.inChunk = false;
         }
-        if (!this.entitySlices[i].remove(entity)) {
+        if (entity.hardCollides()) this.hardCollidingEntities[i].remove(entity); if (!this.entitySlices[i].remove(entity)) { // Paper - optimise hard colliding entities
             return;
         }
         if (entity instanceof EntityItem) {
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 152f613159ef88977de867c0deec94bfa4353f7a..a0249d7a60c1381ebd7131d735a73fa2e9250543 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -211,6 +211,40 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
     }
     // CraftBukkit end
 
+    // Paper start
+    /**
+     * Overriding this field will cause memory leaks.
+     */
+    private final boolean hardCollides;
+
+    private static final java.util.Map<Class<? extends Entity>, Boolean> cachedOverrides = java.util.Collections.synchronizedMap(new java.util.WeakHashMap<>());
+    {
+        Boolean hardCollides = cachedOverrides.get(this.getClass());
+        if (hardCollides == null) {
+            try {
+                Object getHardCollisionBoxMethod = Entity.class.getMethod("ay");
+                Object getHardCollisionBoxEntityMethod = Entity.class.getMethod("j", Entity.class);
+                if (!this.getClass().getMethod("ay").equals(getHardCollisionBoxMethod)) {
+                    hardCollides = Boolean.TRUE;
+                } else if (!this.getClass().getMethod("j", Entity.class).equals(getHardCollisionBoxEntityMethod)) {
+                    hardCollides = Boolean.TRUE;
+                } else {
+                    hardCollides = Boolean.FALSE;
+                }
+                cachedOverrides.put(this.getClass(), hardCollides);
+            } catch (Throwable thr) {
+                // shouldn't happen, just explode
+                throw new RuntimeException(thr);
+            }
+        }
+        this.hardCollides = hardCollides.booleanValue();
+    }
+
+    public final boolean hardCollides() {
+        return this.hardCollides;
+    }
+    // Paper end
+
     public Entity(EntityTypes<?> entitytypes, World world) {
         this.id = Entity.entityCount.incrementAndGet();
         this.passengers = Lists.newArrayList();
diff --git a/src/main/java/net/minecraft/server/EntityEnderDragon.java b/src/main/java/net/minecraft/server/EntityEnderDragon.java
index 96f898acdeae1917a4aaf99ec4a48bccf3904488..73e9859e675902d9fc5942547966b52426a496a2 100644
--- a/src/main/java/net/minecraft/server/EntityEnderDragon.java
+++ b/src/main/java/net/minecraft/server/EntityEnderDragon.java
@@ -844,6 +844,7 @@ public class EntityEnderDragon extends EntityInsentient implements IMonster {
     @Override
     public void checkDespawn() {}
 
+    public final EntityComplexPart[] getComplexParts() { return this.eK(); } // Paper - OBFHELPER
     public EntityComplexPart[] eK() {
         return this.children;
     }
diff --git a/src/main/java/net/minecraft/server/IEntityAccess.java b/src/main/java/net/minecraft/server/IEntityAccess.java
index 74d4c28246e7db850e6d993e07a84b2a6ca24ce2..267a6baae89c181eed545e6758fac7115eb3882f 100644
--- a/src/main/java/net/minecraft/server/IEntityAccess.java
+++ b/src/main/java/net/minecraft/server/IEntityAccess.java
@@ -53,24 +53,36 @@ public interface IEntityAccess {
         return this.b(oclass, axisalignedbb, IEntitySelector.g);
     }
 
+    // Paper start - optimise hard collision
+    /**
+     * Not guaranteed to only return hard colliding entites
+     */
+    default List<Entity> getHardCollidingEntities(@Nullable Entity entity, AxisAlignedBB axisalignedbb, Predicate<Entity> predicate) {
+        return this.getEntities(entity, axisalignedbb, predicate);
+    }
+    // Paper end - optimise hard collision
+
     default Stream<VoxelShape> c(@Nullable Entity entity, AxisAlignedBB axisalignedbb, Predicate<Entity> predicate) {
         if (axisalignedbb.a() < 1.0E-7D) {
             return Stream.empty();
         } else {
             AxisAlignedBB axisalignedbb1 = axisalignedbb.g(1.0E-7D);
 
-            return this.getEntities(entity, axisalignedbb1, predicate.and((entity1) -> {
+            // Paper start
+            Predicate<Entity> effectivePredicate = predicate.and((entity1) -> {
                 return entity == null || !entity.isSameVehicle(entity1);
-            })).stream().flatMap((entity1) -> {
+            });
+
+            return ((entity != null && entity.hardCollides()) ? this.getEntities(entity, axisalignedbb, effectivePredicate) : this.getHardCollidingEntities(entity, axisalignedbb1, effectivePredicate)).stream().flatMap((entity1) -> {
                 if (entity != null) {
-                    AxisAlignedBB axisalignedbb2 = entity.j(entity1);
+                    AxisAlignedBB axisalignedbb2 = entity.j(entity1); // Paper - diff on change, hard collision box method
 
                     if (axisalignedbb2 != null && axisalignedbb2.c(axisalignedbb1)) {
                         return Stream.of(entity1.ay(), axisalignedbb2);
                     }
                 }
 
-                return Stream.of(entity1.ay());
+                return Stream.of(entity1.ay()); // Paper - diff on change, hard collision box method
             }).filter(Objects::nonNull).map(VoxelShapes::a);
         }
     }
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index 418ba04a837ee2b17cc679edd35ba09830c01f28..365539e53efdb7e729b580f52fb23659cbde4f0a 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -1111,6 +1111,32 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
         return this.getChunkAt(i, j, ChunkStatus.FULL, false);
     }
 
+    // Paper start - optimise hard collision handling
+    @Override
+    public List<Entity> getHardCollidingEntities(@Nullable Entity entity, AxisAlignedBB axisalignedbb, Predicate<Entity> predicate) {
+        // copied from below
+        List<Entity> list = Lists.newArrayList();
+        int i = MathHelper.floor((axisalignedbb.minX - 2.0D) / 16.0D);
+        int j = MathHelper.floor((axisalignedbb.maxX + 2.0D) / 16.0D);
+        int k = MathHelper.floor((axisalignedbb.minZ - 2.0D) / 16.0D);
+        int l = MathHelper.floor((axisalignedbb.maxZ + 2.0D) / 16.0D);
+
+        ChunkProviderServer chunkProvider = ((WorldServer)this).getChunkProvider();
+
+        for (int i1 = i; i1 <= j; ++i1) {
+            for (int j1 = k; j1 <= l; ++j1) {
+                Chunk chunk = chunkProvider.getChunkAtIfLoadedMainThread(i1, j1);
+
+                if (chunk != null) {
+                    chunk.getHardCollidingEntities(entity, axisalignedbb, list, predicate);
+                }
+            }
+        }
+
+        return list;
+    }
+    // Paper end - optimise hard collision handling
+
     @Override
     public List<Entity> getEntities(@Nullable Entity entity, AxisAlignedBB axisalignedbb, @Nullable Predicate<? super Entity> predicate) {
         this.getMethodProfiler().c("getEntities");