Paper/Spigot-Server-Patches/0542-Optimize-Pathfinder-Remove-Streams-Optimized-collect.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Tue, 4 Aug 2020 22:24:15 +0200
Subject: [PATCH] Optimize Pathfinder - Remove Streams / Optimized collections

I utilized the IDE to convert streams to non streams code, so shouldn't
be any risk of behavior change. Only did minor optimization of the
generated code set to remove unnecessary things.

I expect us to just drop this patch on next major update and re-apply
it with the IDE again and re-apply the collections optimization.

Optimize collection by creating a list instead of a set of the key and value.

This lets us get faster foreach iteration, as well as avoids map lookups on
the values when needed.

diff --git a/src/main/java/net/minecraft/server/Pathfinder.java b/src/main/java/net/minecraft/server/Pathfinder.java
index b31d1f73ce0f067e352868b53eab7557c34b17eb..997982136cdd2a0d922e501473e0d4d1aabf567a 100644
--- a/src/main/java/net/minecraft/server/Pathfinder.java
+++ b/src/main/java/net/minecraft/server/Pathfinder.java
@@ -30,9 +30,12 @@ public class Pathfinder {
         this.d.a();
         this.c.a(chunkcache, entityinsentient);
         PathPoint pathpoint = this.c.b();
-        Map<PathDestination, BlockPosition> map = (Map) set.stream().collect(Collectors.toMap((blockposition) -> {
-            return this.c.a((double) blockposition.getX(), (double) blockposition.getY(), (double) blockposition.getZ());
-        }, Function.identity()));
+        // Paper start - remove streams - and optimize collection
+        List<Map.Entry<PathDestination, BlockPosition>> map = Lists.newArrayList();
+        for (BlockPosition blockposition : set) {
+            map.add(new java.util.AbstractMap.SimpleEntry<>(this.c.a((double) blockposition.getX(), blockposition.getY(), blockposition.getZ()), blockposition));
+        }
+        // Paper end
         PathEntity pathentity = this.a(pathpoint, map, f, i, f1);
 
         this.c.a();
@@ -40,17 +43,17 @@ public class Pathfinder {
     }
 
     @Nullable
-    private PathEntity a(PathPoint pathpoint, Map<PathDestination, BlockPosition> map, float f, int i, float f1) {
-        Set<PathDestination> set = map.keySet();
+    private PathEntity a(PathPoint pathpoint, List<Map.Entry<PathDestination, BlockPosition>> list, float f, int i, float f1) { // Paper - optimize collection
+        //Set<PathDestination> set = map.keySet(); // Paper
 
         pathpoint.e = 0.0F;
-        pathpoint.f = this.a(pathpoint, set);
+        pathpoint.f = this.a(pathpoint, list); // Paper - optimize collection
         pathpoint.g = pathpoint.f;
         this.d.a();
         this.d.a(pathpoint);
         Set<PathPoint> set1 = ImmutableSet.of();
         int j = 0;
-        Set<PathDestination> set2 = Sets.newHashSetWithExpectedSize(set.size());
+        List<Map.Entry<PathDestination, BlockPosition>> set2 = Lists.newArrayListWithExpectedSize(list.size()); // Paper - optimize collection
         int k = (int) ((float) this.b * f1);
 
         while (!this.d.e()) {
@@ -62,14 +65,15 @@ public class Pathfinder {
             PathPoint pathpoint1 = this.d.c();
 
             pathpoint1.i = true;
-            Iterator iterator = set.iterator();
-
-            while (iterator.hasNext()) {
-                PathDestination pathdestination = (PathDestination) iterator.next();
+            // Paper start - optimize collection
+            for (int i1 = 0; i1 < list.size(); i1++) {
+                Map.Entry<PathDestination, BlockPosition> entry = list.get(i1);
+                PathDestination pathdestination = entry.getKey();
 
                 if (pathpoint1.c((PathPoint) pathdestination) <= (float) i) {
                     pathdestination.e();
-                    set2.add(pathdestination);
+                    set2.add(entry);
+                    // Paper end
                 }
             }
 
@@ -90,7 +94,7 @@ public class Pathfinder {
                     if (pathpoint2.j < f && (!pathpoint2.c() || f3 < pathpoint2.e)) {
                         pathpoint2.h = pathpoint1;
                         pathpoint2.e = f3;
-                        pathpoint2.f = this.a(pathpoint2, set) * 1.5F;
+                        pathpoint2.f = this.a(pathpoint2, list) * 1.5F; // Paper - list instead of set
                         if (pathpoint2.c()) {
                             this.d.a(pathpoint2, pathpoint2.e + pathpoint2.f);
                         } else {
@@ -102,28 +106,29 @@ public class Pathfinder {
             }
         }
 
-        Optional<PathEntity> optional = !set2.isEmpty() ? set2.stream().map((pathdestination1) -> {
-            return this.a(pathdestination1.d(), (BlockPosition) map.get(pathdestination1), true);
-        }).min(Comparator.comparingInt(PathEntity::e)) : set.stream().map((pathdestination1) -> {
-            return this.a(pathdestination1.d(), (BlockPosition) map.get(pathdestination1), false);
-        }).min(Comparator.comparingDouble(PathEntity::n).thenComparingInt(PathEntity::e));
-
-        if (!optional.isPresent()) {
-            return null;
-        } else {
-            PathEntity pathentity = (PathEntity) optional.get();
-
-            return pathentity;
+        // Paper start - remove streams - and optimize collection
+        PathEntity best = null;
+        boolean useSet1 = set2.isEmpty();
+        Comparator<PathEntity> comparator = useSet1 ? Comparator.comparingInt(PathEntity::e)
+            : Comparator.comparingDouble(PathEntity::n).thenComparingInt(PathEntity::e);
+        for (Map.Entry<PathDestination, BlockPosition> entry : useSet1 ? list : set2) {
+            PathEntity pathEntity = this.a(entry.getKey().d(), entry.getValue(), !useSet1);
+            if (best == null || comparator.compare(pathEntity, best) < 0)
+                best = pathEntity;
         }
+        return best;
+        // Paper end
     }
 
-    private float a(PathPoint pathpoint, Set<PathDestination> set) {
+    private float a(PathPoint pathpoint, List<Map.Entry<PathDestination, BlockPosition>> list) { // Paper - optimize collection
         float f = Float.MAX_VALUE;
 
         float f1;
 
-        for (Iterator iterator = set.iterator(); iterator.hasNext(); f = Math.min(f1, f)) {
-            PathDestination pathdestination = (PathDestination) iterator.next();
+        // Paper start - optimize collection
+        for (int i = 0, listSize = list.size(); i < listSize; f = Math.min(f1, f), i++) { // Paper
+            PathDestination pathdestination = list.get(i).getKey(); // Paper
+            // Paper end
 
             f1 = pathpoint.a(pathdestination);
             pathdestination.a(f1, pathpoint);