PaperMC/patches/server/0389-Optimise-ArraySetSorted-removeIf.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Wed, 15 Apr 2020 18:23:28 -0700
Subject: [PATCH] Optimise ArraySetSorted#removeIf

Remove iterator allocation and ensure the call is always O(n)

diff --git a/src/main/java/net/minecraft/server/level/DistanceManager.java b/src/main/java/net/minecraft/server/level/DistanceManager.java
index 6228f2f67541da62b0ae093de987662db9643740..8376439e36f0f75779d0fbefbe50b215a40c42aa 100644
--- a/src/main/java/net/minecraft/server/level/DistanceManager.java
+++ b/src/main/java/net/minecraft/server/level/DistanceManager.java
@@ -86,13 +86,27 @@ public abstract class DistanceManager {
     protected void purgeStaleTickets() {
         ++this.ticketTickCounter;
         ObjectIterator objectiterator = this.tickets.long2ObjectEntrySet().fastIterator();
+        // Paper start - use optimised removeIf
+        long[] currChunk = new long[1];
+        long ticketCounter = DistanceManager.this.ticketTickCounter;
+        java.util.function.Predicate<Ticket<?>> removeIf = (ticket) -> {
+            final boolean ret = ticket.timedOut(ticketCounter);
+            if (ret) {
+                this.tickingTicketsTracker.removeTicket(currChunk[0], ticket);
+            }
+            return ret;
+        };
+        // Paper end - use optimised removeIf
 
         while (objectiterator.hasNext()) {
             Entry<SortedArraySet<Ticket<?>>> entry = (Entry) objectiterator.next();
-            Iterator<Ticket<?>> iterator = ((SortedArraySet) entry.getValue()).iterator();
-            boolean flag = false;
+            // Paper start - use optimised removeIf
+            Iterator<Ticket<?>> iterator = null;
+            currChunk[0] = entry.getLongKey();
+            boolean flag = entry.getValue().removeIf(removeIf);
 
-            while (iterator.hasNext()) {
+            while (false && iterator.hasNext()) {
+                // Paper end - use optimised removeIf
                 Ticket<?> ticket = (Ticket) iterator.next();
 
                 if (ticket.timedOut(this.ticketTickCounter)) {
diff --git a/src/main/java/net/minecraft/util/SortedArraySet.java b/src/main/java/net/minecraft/util/SortedArraySet.java
index d1b2ba24ef54e01c6249c3b2ca16e80f03c001a6..5f1c4c6b9e36f2d6ec43b82cc0e2cae24b800dc4 100644
--- a/src/main/java/net/minecraft/util/SortedArraySet.java
+++ b/src/main/java/net/minecraft/util/SortedArraySet.java
@@ -22,6 +22,41 @@ public class SortedArraySet<T> extends AbstractSet<T> {
             this.contents = (T[])castRawArray(new Object[initialCapacity]);
         }
     }
+    // Paper start - optimise removeIf
+    @Override
+    public boolean removeIf(java.util.function.Predicate<? super T> filter) {
+        // prev. impl used an iterator, which could be n^2 and creates garbage
+        int i = 0, len = this.size;
+        T[] backingArray = this.contents;
+
+        for (;;) {
+            if (i >= len) {
+                return false;
+            }
+            if (!filter.test(backingArray[i])) {
+                ++i;
+                continue;
+            }
+            break;
+        }
+
+        // we only want to write back to backingArray if we really need to
+
+        int lastIndex = i; // this is where new elements are shifted to
+
+        for (; i < len; ++i) {
+            T curr = backingArray[i];
+            if (!filter.test(curr)) { // if test throws we're screwed
+                backingArray[lastIndex++] = curr;
+            }
+        }
+
+        // cleanup end
+        Arrays.fill(backingArray, lastIndex, len, null);
+        this.size = lastIndex;
+        return true;
+    }
+    // Paper end - optimise removeIf
 
     public static <T extends Comparable<T>> SortedArraySet<T> create() {
         return create(10);