From 6ebb700be04e6c4b6548dacb7889df46ffebcb6c Mon Sep 17 00:00:00 2001
From: Brian Neumann-Fopiano <mypsn1550@gmail.com>
Date: Wed, 21 Oct 2026 19:29:37 -0400
Subject: [PATCH] Reuse cave biome cache

- Carve scratch keeps one cave biome cache per thread, cleared per chunk
---
 .../art/arcane/iris/generation/stage/IrisCarveModifier.java    | 2 +-
 .../art/arcane/iris/generation/stage/IrisCarveScratch.java     | 3 +++
 .../art/arcane/iris/generation/stage/IrisCarveScratchTest.java | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/art/arcane/iris/generation/stage/IrisCarveModifier.java b/core/src/main/java/art/arcane/iris/generation/stage/IrisCarveModifier.java
index ced2742a0..4a09bc530 100644
--- a/core/src/main/java/art/arcane/iris/generation/stage/IrisCarveModifier.java
+++ b/core/src/main/java/art/arcane/iris/generation/stage/IrisCarveModifier.java
@@ -102,9 +102,9 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
         PrecisionStopwatch caveStopwatch = PrecisionStopwatch.start();
         Mantle<Matter> mantle = getEngine().getMantle().getMantle();
         CaveInputs resolverState = new CaveInputs(getEngine());
-        Long2ObjectOpenHashMap<IrisBiome> caveBiomeCache = new Long2ObjectOpenHashMap<>(2048);
         IrisCarveScratch scratch = SCRATCH.get();
         scratch.reset();
+        Long2ObjectOpenHashMap<IrisBiome> caveBiomeCache = scratch.caveBiomeCache;
         CarveWallBuffer walls = scratch.walls;
         CarveColumnMask[] columnMasks = scratch.columnMasks;
         CarveColumnMask[] boundaryMasks = scratch.boundaryMasks;
diff --git a/core/src/main/java/art/arcane/iris/generation/stage/IrisCarveScratch.java b/core/src/main/java/art/arcane/iris/generation/stage/IrisCarveScratch.java
index e75522d11..6dfd76d6f 100644
--- a/core/src/main/java/art/arcane/iris/generation/stage/IrisCarveScratch.java
+++ b/core/src/main/java/art/arcane/iris/generation/stage/IrisCarveScratch.java
@@ -21,6 +21,7 @@ package art.arcane.iris.generation.stage;
 import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.volmlib.util.matter.MatterCavern;
 import art.arcane.volmlib.util.math.PowerOfTwoCoordinates;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 
 import java.util.Arrays;
 import java.util.HashMap;
@@ -32,6 +33,7 @@ final class IrisCarveScratch {
     final int[] surfaceHeights = new int[256];
     final CarveWallBuffer walls = new CarveWallBuffer(512);
     final Map<String, IrisBiome> customBiomeCache = new HashMap<>();
+    final Long2ObjectOpenHashMap<IrisBiome> caveBiomeCache = new Long2ObjectOpenHashMap<>(4096);
     int[] upperSurfaceHeights;
     boolean customCaveBiomePresent;
 
@@ -56,6 +58,7 @@ final class IrisCarveScratch {
         }
         walls.clear();
         customBiomeCache.clear();
+        caveBiomeCache.clear();
         customCaveBiomePresent = false;
     }
 }
diff --git a/core/src/test/java/art/arcane/iris/generation/stage/IrisCarveScratchTest.java b/core/src/test/java/art/arcane/iris/generation/stage/IrisCarveScratchTest.java
index b979d3f63..bfe93fb0c 100644
--- a/core/src/test/java/art/arcane/iris/generation/stage/IrisCarveScratchTest.java
+++ b/core/src/test/java/art/arcane/iris/generation/stage/IrisCarveScratchTest.java
@@ -1,5 +1,6 @@
 package art.arcane.iris.generation.stage;
 
+import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.volmlib.util.matter.MatterCavern;
 import org.junit.Test;
 
@@ -49,6 +50,7 @@ public class IrisCarveScratchTest {
         scratch.boundaryMasks[0].add(13);
         scratch.walls.put(1, 12, 2, cavern);
         scratch.customBiomeCache.put("cave", null);
+        scratch.caveBiomeCache.put(42L, new IrisBiome());
         scratch.customCaveBiomePresent = true;
 
         scratch.reset();
@@ -56,6 +58,7 @@ public class IrisCarveScratchTest {
         assertTrue(scratch.columnMasks[0].isEmpty());
         assertTrue(scratch.boundaryMasks[0].isEmpty());
         assertTrue(scratch.customBiomeCache.isEmpty());
+        assertTrue(scratch.caveBiomeCache.isEmpty());
         assertFalse(scratch.customCaveBiomePresent);
         int[] wallCount = new int[1];
         scratch.walls.forEach((x, y, z, value) -> wallCount[0]++);