From 7a5a9791699968c05383f97b105870149b425169 Mon Sep 17 00:00:00 2001
From: DBotThePony <dbotthepony@yandex.ru>
Date: Wed, 26 Mar 2025 13:15:26 +0700
Subject: [PATCH] Improve enhanced placed feature performance

---
 .../mc/otm/worldgen/EnhancedPlacedFeature.kt  | 28 +++++++++++++------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/src/main/kotlin/ru/dbotthepony/mc/otm/worldgen/EnhancedPlacedFeature.kt b/src/main/kotlin/ru/dbotthepony/mc/otm/worldgen/EnhancedPlacedFeature.kt
index dc9c245a4..3f9483e91 100644
--- a/src/main/kotlin/ru/dbotthepony/mc/otm/worldgen/EnhancedPlacedFeature.kt
+++ b/src/main/kotlin/ru/dbotthepony/mc/otm/worldgen/EnhancedPlacedFeature.kt
@@ -3,13 +3,11 @@ package ru.dbotthepony.mc.otm.worldgen
 import com.github.benmanes.caffeine.cache.Cache
 import com.github.benmanes.caffeine.cache.Caffeine
 import com.github.benmanes.caffeine.cache.Scheduler
-import com.mojang.datafixers.util.Either
-import com.mojang.datafixers.util.Pair
 import com.mojang.serialization.Codec
-import com.mojang.serialization.DataResult
-import com.mojang.serialization.DynamicOps
 import com.mojang.serialization.codecs.RecordCodecBuilder
+import it.unimi.dsi.fastutil.ints.Int2ObjectRBTreeMap
 import it.unimi.dsi.fastutil.io.FastByteArrayOutputStream
+import it.unimi.dsi.fastutil.objects.ObjectArrayList
 import it.unimi.dsi.fastutil.objects.ObjectRBTreeSet
 import net.minecraft.Util
 import net.minecraft.core.BlockPos
@@ -23,15 +21,16 @@ import net.minecraft.world.level.levelgen.feature.Feature
 import net.minecraft.world.level.levelgen.feature.FeaturePlaceContext
 import net.minecraft.world.level.levelgen.feature.configurations.FeatureConfiguration
 import net.minecraft.world.level.levelgen.placement.PlacedFeature
-import net.minecraft.world.level.levelgen.placement.PlacementModifier
 import ru.dbotthepony.kommons.util.XXHash64
+import ru.dbotthepony.mc.otm.THREAD_LOCAL_RANDOM
+import ru.dbotthepony.mc.otm.core.shuffle
 import ru.dbotthepony.mc.otm.core.util.GJRAND64RandomSource
 import ru.dbotthepony.mc.otm.data.codec.minRange
 import ru.dbotthepony.mc.otm.worldgen.feature.EnhancedFeature
 import ru.dbotthepony.mc.otm.worldgen.placement.EnhancedPlacement
 import java.io.DataOutputStream
 import java.time.Duration
-import java.util.LinkedList
+import java.util.*
 import kotlin.math.sqrt
 
 object EnhancedPlacedFeature : Feature<EnhancedPlacedFeature.Config>(
@@ -137,7 +136,7 @@ object EnhancedPlacedFeature : Feature<EnhancedPlacedFeature.Config>(
 		fun place(context: FeaturePlaceContext<*>): Boolean {
 			val cache = getCache(context.level())
 			val chunkPos = ChunkPos(context.origin())
-			val instances = ArrayList<GeneratedChunk>()
+			val chunkPositions = ArrayList<ChunkPos>()
 
 			for (x in -chunkScanRange .. chunkScanRange) {
 				for (z in -chunkScanRange .. chunkScanRange) {
@@ -146,13 +145,24 @@ object EnhancedPlacedFeature : Feature<EnhancedPlacedFeature.Config>(
 
 					if (radius <= chunkScanRange) {
 						val thisPos = ChunkPos(chunkPos.x + x, chunkPos.z + z)
-						instances.add(cache.get(thisPos) { evaluate(context, thisPos) })
+						chunkPositions.add(thisPos)
 					}
 				}
 			}
 
+			val withIndex = ObjectArrayList(chunkPositions.withIndex().iterator())
+			// evaluate chunks in random order, so in multithreaded environments we experience less congestion
+			// between threads which lookup cache while it is being populated on neighbouring chunks
+			withIndex.shuffle(THREAD_LOCAL_RANDOM)
+
+			val instances = Int2ObjectRBTreeMap<GeneratedChunk>()
+
+			withIndex.forEach { (i, it) ->
+				instances.put(i, cache.get(it) { evaluate(context, it) })
+			}
+
 			var any = false
-			instances.forEach { any = it.place(context) }
+			instances.values.forEach { any = it.place(context) }
 			return any
 		}
 	}