From 779c16a7b1360256e47ea557c27bdab3f6543a58 Mon Sep 17 00:00:00 2001
From: CullanP <cullanpage@gmail.com>
Date: Thu, 11 Feb 2016 21:43:17 -0700
Subject: [PATCH] Avoid hopper searches if there are no items

Hoppers searching for items and minecarts is the most expensive part of hopper ticking.
We keep track of the number of minecarts and items in a chunk.
If there are no items in the chunk, we skip searching for items.
If there are no minecarts in the chunk, we skip searching for them.

Usually hoppers aren't near items, so we can skip most item searches.
And since minecart hoppers are used _very_ rarely near we can avoid alot of searching there.

Combined, this adds up a lot.

diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
index c636da3..aa555f5 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -34,6 +34,11 @@ public class Chunk {
     private boolean k;
     public final Map<BlockPosition, TileEntity> tileEntities;
     public final List<Entity>[] entitySlices; // Spigot
+    // PaperSpigot start - track the number of minecarts and items
+    // Keep this synced with entitySlices.add() and entitySlices.remove()
+    private final int[] itemCounts = new int[16];
+    private final int[] inventoryEntityCounts = new int[16];
+    // PaperSpigot end
     private boolean done;
     private boolean lit;
     private boolean p;
@@ -735,6 +740,13 @@ public class Chunk {
         entity.af = k;
         entity.ag = this.locZ;
         this.entitySlices[k].add(entity);
+        // PaperSpigot start - update counts
+        if (entity instanceof EntityItem) {
+            itemCounts[k]++;
+        } else if (entity instanceof IInventory) {
+            inventoryEntityCounts[k]++;
+        }
+        // PaperSpigot end
         // Spigot start - increment creature type count
         // Keep this synced up with World.a(Class)
         if (entity instanceof EntityInsentient) {
@@ -767,6 +779,13 @@ public class Chunk {
         }
 
         this.entitySlices[i].remove(entity);
+        // PaperSpigot start - update counts
+        if (entity instanceof EntityItem) {
+            itemCounts[i]--;
+        } else if (entity instanceof IInventory) {
+            inventoryEntityCounts[i]--;
+        }
+        // PaperSpigot end
         // Spigot start - decrement creature type count
         // Keep this synced up with World.a(Class)
         if (entity instanceof EntityInsentient) {
@@ -955,7 +974,15 @@ public class Chunk {
         for (int k = i; k <= j; ++k) {
             if (!this.entitySlices[k].isEmpty()) {
                 Iterator iterator = this.entitySlices[k].iterator();
-
+                // PaperSpigot start - Don't search for inventories if we have none, and that is all we want
+                /*
+                 * We check if they want inventories by seeing if it is the static `IEntitySelector.c`
+                 *
+                 * Make sure the inventory selector stays in sync.
+                 * It should be the one that checks `var1 instanceof IInventory && var1.isAlive()`
+                 */
+                if (predicate == IEntitySelector.c && inventoryEntityCounts[k] <= 0) continue;
+                // PaperSpigot end
                 while (iterator.hasNext()) {
                     Entity entity1 = (Entity) iterator.next();
 
@@ -988,7 +1015,18 @@ public class Chunk {
         i = MathHelper.clamp(i, 0, this.entitySlices.length - 1);
         j = MathHelper.clamp(j, 0, this.entitySlices.length - 1);
 
+        // PaperSpigot start
+        int[] counts;
+        if (ItemStack.class.isAssignableFrom(oclass)) {
+            counts = itemCounts;
+        } else if (IInventory.class.isAssignableFrom(oclass)) {
+            counts = inventoryEntityCounts;
+        } else {
+            counts = null;
+        }
+        // PaperSpigot end
         for (int k = i; k <= j; ++k) {
+            if (counts != null && counts[k] <= 0) continue; // PaperSpigot - Don't check a chunk if it doesn't have the type we are looking for
             Iterator iterator = this.entitySlices[k].iterator(); // Spigot
 
             while (iterator.hasNext()) {
-- 
2.7.1