From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sat, 23 Sep 2023 23:15:52 -0700
Subject: [PATCH] Optimise nearby player retrieval

Instead of searching/testing every player online on the server,
we can instead use the nearby player tracking system to reduce
the number of tests per search.

diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -0,0 +0,0 @@ public class ServerLevel extends Level implements WorldGenLevel {
         this.lagCompensationTick = (System.nanoTime() - net.minecraft.server.MinecraftServer.SERVER_INIT) / (java.util.concurrent.TimeUnit.MILLISECONDS.toNanos(50L));
     }
     // Paper end - lag compensation
+    // Paper start - optimise nearby player retrieval
+    @Override
+    public java.util.List<net.minecraft.world.entity.player.Player> getNearbyPlayers(net.minecraft.world.entity.ai.targeting.TargetingConditions targetPredicate,
+                                                                                     net.minecraft.world.entity.LivingEntity entity,
+                                                                                     net.minecraft.world.phys.AABB box) {
+        return this.getNearbyEntities(Player.class, targetPredicate, entity, box);
+    }
+
+    @Override
+    public Player getNearestPlayer(double x, double y, double z, double maxDistance, @Nullable Predicate<Entity> targetPredicate) {
+        if (maxDistance > 0.0D) {
+            io.papermc.paper.util.player.NearbyPlayers players = this.chunkSource.chunkMap.getNearbyPlayers();
+
+            com.destroystokyo.paper.util.maplist.ReferenceList<ServerPlayer> nearby = players.getPlayersByBlock(
+                io.papermc.paper.util.CoordinateUtils.getBlockCoordinate(x),
+                io.papermc.paper.util.CoordinateUtils.getBlockCoordinate(z),
+                io.papermc.paper.util.player.NearbyPlayers.NearbyMapType.GENERAL
+            );
+
+            if (nearby == null) {
+                return null;
+            }
+
+            ServerPlayer nearest = null;
+            double nearestDist = maxDistance * maxDistance;
+            Object[] rawData = nearby.getRawData();
+            for (int i = 0, len = nearby.size(); i < len; ++i) {
+                ServerPlayer player = (ServerPlayer)rawData[i];
+                double dist = player.distanceToSqr(x, y, z);
+                if (dist >= nearestDist) {
+                    continue;
+                }
+
+                if (targetPredicate == null || targetPredicate.test(player)) {
+                    nearest = player;
+                    nearestDist = dist;
+                }
+            }
+
+            return nearest;
+        } else {
+            ServerPlayer nearest = null;
+            double nearestDist = Double.MAX_VALUE;
+
+            for (ServerPlayer player : this.players()) {
+                double dist = player.distanceToSqr(x, y, z);
+                if (dist >= nearestDist) {
+                    continue;
+                }
+
+                if (targetPredicate == null || targetPredicate.test(player)) {
+                    nearest = player;
+                    nearestDist = dist;
+                }
+            }
+
+            return nearest;
+        }
+    }
+
+    @Override
+    public Player getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions targetPredicate, LivingEntity entity) {
+        return this.getNearestPlayer(targetPredicate, entity, entity.getX(), entity.getY(), entity.getZ());
+    }
+
+    @Override
+    public Player getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions targetPredicate, LivingEntity entity,
+                                   double x, double y, double z) {
+        double range = targetPredicate.range;
+        if (range > 0.0D) {
+            io.papermc.paper.util.player.NearbyPlayers players = this.chunkSource.chunkMap.getNearbyPlayers();
+
+            com.destroystokyo.paper.util.maplist.ReferenceList<ServerPlayer> nearby = players.getPlayersByBlock(
+                io.papermc.paper.util.CoordinateUtils.getBlockCoordinate(x),
+                io.papermc.paper.util.CoordinateUtils.getBlockCoordinate(z),
+                io.papermc.paper.util.player.NearbyPlayers.NearbyMapType.GENERAL
+            );
+
+            if (nearby == null) {
+                return null;
+            }
+
+            ServerPlayer nearest = null;
+            double nearestDist = Double.MAX_VALUE;
+            Object[] rawData = nearby.getRawData();
+            for (int i = 0, len = nearby.size(); i < len; ++i) {
+                ServerPlayer player = (ServerPlayer)rawData[i];
+                double dist = player.distanceToSqr(x, y, z);
+                if (dist >= nearestDist) {
+                    continue;
+                }
+
+                if (targetPredicate.test(entity, player)) {
+                    nearest = player;
+                    nearestDist = dist;
+                }
+            }
+
+            return nearest;
+        } else {
+            return this.getNearestEntity(this.players(), targetPredicate, entity, x, y, z);
+        }
+    }
+
+    @Nullable
+    public Player getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions targetPredicate, double x, double y, double z) {
+        return this.getNearestPlayer(targetPredicate, null, x, y, z);
+    }
+    // Paper end - optimise nearby player retrieval
 
     // Add env and gen to constructor, IWorldDataServer -> WorldDataServer
     public ServerLevel(MinecraftServer minecraftserver, Executor executor, LevelStorageSource.LevelStorageAccess convertable_conversionsession, PrimaryLevelData iworlddataserver, ResourceKey<Level> resourcekey, LevelStem worlddimension, ChunkProgressListener worldloadlistener, boolean flag, long i, List<CustomSpawner> list, boolean flag1, @Nullable RandomSequences randomsequences, org.bukkit.World.Environment env, org.bukkit.generator.ChunkGenerator gen, org.bukkit.generator.BiomeProvider biomeProvider) {
diff --git a/src/main/java/net/minecraft/world/entity/ai/sensing/PlayerSensor.java b/src/main/java/net/minecraft/world/entity/ai/sensing/PlayerSensor.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/entity/ai/sensing/PlayerSensor.java
+++ b/src/main/java/net/minecraft/world/entity/ai/sensing/PlayerSensor.java
@@ -0,0 +0,0 @@ public class PlayerSensor extends Sensor<LivingEntity> {
 
     @Override
     protected void doTick(ServerLevel world, LivingEntity entity) {
-        List<Player> list = world.players()
-            .stream()
-            .filter(EntitySelector.NO_SPECTATORS)
-            .filter(player -> entity.closerThan(player, 16.0))
-            .sorted(Comparator.comparingDouble(entity::distanceToSqr))
-            .collect(Collectors.toList());
+        // Paper start - Perf: optimise nearby player retrieval & remove streams from hot code
+        io.papermc.paper.util.player.NearbyPlayers nearbyPlayers = world.chunkSource.chunkMap.getNearbyPlayers();
+        net.minecraft.world.phys.Vec3 entityPos = entity.position();
+        com.destroystokyo.paper.util.maplist.ReferenceList<net.minecraft.server.level.ServerPlayer> nearby = nearbyPlayers.getPlayersByChunk(
+            entity.chunkPosition().x,
+            entity.chunkPosition().z,
+            io.papermc.paper.util.player.NearbyPlayers.NearbyMapType.GENERAL_REALLY_SMALL
+        );
+
+        List<Player> players = new java.util.ArrayList<>(nearby == null ? 0 : nearby.size());
+        if (nearby != null) {
+            Object[] rawData = nearby.getRawData();
+            for (int index = 0, len = nearby.size(); index < len; ++index) {
+                net.minecraft.server.level.ServerPlayer player = (net.minecraft.server.level.ServerPlayer) rawData[index];
+                if (player.isSpectator()) {
+                    continue;
+                }
+                if (player.distanceToSqr(entityPos.x, entityPos.y, entityPos.z) >= (16.0 * 16.0)) {
+                    continue;
+                }
+                players.add(player);
+            }
+        }
+        players.sort(Comparator.comparingDouble(entity::distanceToSqr));
         Brain<?> brain = entity.getBrain();
-        brain.setMemory(MemoryModuleType.NEAREST_PLAYERS, list);
-        List<Player> list2 = list.stream().filter(player -> isEntityTargetable(entity, player)).collect(Collectors.toList());
-        brain.setMemory(MemoryModuleType.NEAREST_VISIBLE_PLAYER, list2.isEmpty() ? null : list2.get(0));
-        Optional<Player> optional = list2.stream().filter(player -> isEntityAttackable(entity, player)).findFirst();
-        brain.setMemory(MemoryModuleType.NEAREST_VISIBLE_ATTACKABLE_PLAYER, optional);
+
+        brain.setMemory(MemoryModuleType.NEAREST_PLAYERS, players);
+
+        Player firstTargetable = null;
+        Player firstAttackable = null;
+        for (Player player : players) {
+            if (firstTargetable == null && Sensor.isEntityTargetable(entity, player)) {
+                firstTargetable = player;
+            }
+            if (firstAttackable == null && Sensor.isEntityAttackable(entity, player)) {
+                firstAttackable = player;
+            }
+
+            if (firstAttackable != null && firstTargetable != null) {
+                break;
+            }
+        }
+        brain.setMemory(MemoryModuleType.NEAREST_VISIBLE_PLAYER, firstTargetable);
+        brain.setMemory(MemoryModuleType.NEAREST_VISIBLE_ATTACKABLE_PLAYER, Optional.ofNullable(firstAttackable));
+        // Paper end - Perf: optimise nearby player retrieval & remove streams from hot code
     }
 }
diff --git a/src/main/java/net/minecraft/world/entity/ai/targeting/TargetingConditions.java b/src/main/java/net/minecraft/world/entity/ai/targeting/TargetingConditions.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/entity/ai/targeting/TargetingConditions.java
+++ b/src/main/java/net/minecraft/world/entity/ai/targeting/TargetingConditions.java
@@ -0,0 +0,0 @@ public class TargetingConditions {
     public static final TargetingConditions DEFAULT = forCombat();
     private static final double MIN_VISIBILITY_DISTANCE_FOR_INVISIBLE_TARGET = 2.0;
     private final boolean isCombat;
-    private double range = -1.0;
+    public double range = -1.0; // Paper - public
     private boolean checkLineOfSight = true;
     private boolean testInvisible = true;
     @Nullable
diff --git a/src/main/java/net/minecraft/world/level/EntityGetter.java b/src/main/java/net/minecraft/world/level/EntityGetter.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/EntityGetter.java
+++ b/src/main/java/net/minecraft/world/level/EntityGetter.java
@@ -0,0 +0,0 @@ public interface EntityGetter {
         T livingEntity = null;
 
         for (T livingEntity2 : entityList) {
+            // Paper start - optimise nearby player retrieval; move up
+            // don't check entities outside closest range
+            double e = livingEntity2.distanceToSqr(x, y, z);
+            if (d == -1.0 || e < d) {
+            // Paper end - move up
             if (targetPredicate.test(entity, livingEntity2)) {
-                double e = livingEntity2.distanceToSqr(x, y, z);
-                if (d == -1.0 || e < d) {
+                // Paper - optimise nearby player retrieval; move up
                     d = e;
                     livingEntity = livingEntity2;
                 }
