Paper/patches/server-remapped/0539-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/world/level/pathfinder/PathFinder.java b/src/main/java/net/minecraft/world/level/pathfinder/PathFinder.java
index ba8ee93032aabe7ec4ecf52d452e1a580d6ebc20..2ef0e04af771e14f8d71aef4ccb81d3b81db7df5 100644
--- a/src/main/java/net/minecraft/world/level/pathfinder/PathFinder.java
+++ b/src/main/java/net/minecraft/world/level/pathfinder/PathFinder.java
@@ -33,28 +33,31 @@ public class PathFinder {
         this.openSet.a();
         this.nodeEvaluator.prepare(world, mob);
         Node pathpoint = this.nodeEvaluator.getStart();
-        Map<Target, BlockPos> map = (Map) positions.stream().collect(Collectors.toMap((blockposition) -> {
-            return this.nodeEvaluator.getGoal((double) blockposition.getX(), (double) blockposition.getY(), (double) blockposition.getZ());
-        }, Function.identity()));
-        Path pathentity = this.findPath(pathpoint, map, followRange, distance, rangeMultiplier);
+        // Paper start - remove streams - and optimize collection
+        List<Map.Entry<Target, BlockPos>> map = Lists.newArrayList();
+        for (BlockPos blockposition : positions) {
+            map.add(new java.util.AbstractMap.SimpleEntry<>(this.nodeEvaluator.getGoal((double) blockposition.getX(), blockposition.getY(), blockposition.getZ()), blockposition));
+        }
+        // Paper end
+        Path pathentity = this.a(pathpoint, map, followRange, distance, rangeMultiplier);
 
         this.nodeEvaluator.done();
         return pathentity;
     }
 
     @Nullable
-    private Path findPath(Node startNode, Map<Target, BlockPos> positions, float followRange, int distance, float rangeMultiplier) {
-        Set<Target> set = positions.keySet();
+    private Path a(Node pathpoint, List<Map.Entry<Target, BlockPos>> list, float f, int i, float f1) { // Paper - optimize collection
+        //Set<PathDestination> set = map.keySet(); // Paper
 
-        startNode.g = 0.0F;
-        startNode.h = this.getBestH(startNode, set);
-        startNode.f = startNode.h;
+        pathpoint.g = 0.0F;
+        pathpoint.h = this.a(pathpoint, list); // Paper - optimize collection
+        pathpoint.f = pathpoint.h;
         this.openSet.a();
-        this.openSet.a(startNode);
+        this.openSet.a(pathpoint);
         Set<Node> set1 = ImmutableSet.of();
         int j = 0;
-        Set<Target> set2 = Sets.newHashSetWithExpectedSize(set.size());
-        int k = (int) ((float) this.maxVisitedNodes * rangeMultiplier);
+        List<Map.Entry<Target, BlockPos>> set2 = Lists.newArrayListWithExpectedSize(list.size()); // Paper - optimize collection
+        int k = (int) ((float) this.maxVisitedNodes * f1);
 
         while (!this.openSet.e()) {
             ++j;
@@ -65,14 +68,15 @@ public class PathFinder {
             Node pathpoint1 = this.openSet.c();
 
             pathpoint1.closed = true;
-            Iterator iterator = set.iterator();
-
-            while (iterator.hasNext()) {
-                Target pathdestination = (Target) iterator.next();
+            // Paper start - optimize collection
+            for (int i1 = 0; i1 < list.size(); i1++) {
+                Map.Entry<Target, BlockPos> entry = list.get(i1);
+                Target pathdestination = entry.getKey();
 
-                if (pathpoint1.distanceManhattan((Node) pathdestination) <= (float) distance) {
+                if (pathpoint1.distanceManhattan((Node) pathdestination) <= (float) i) {
                     pathdestination.setReached();
-                    set2.add(pathdestination);
+                    set2.add(entry);
+                    // Paper end
                 }
             }
 
@@ -80,7 +84,7 @@ public class PathFinder {
                 break;
             }
 
-            if (pathpoint1.distanceTo(startNode) < followRange) {
+            if (pathpoint1.distanceTo(pathpoint) < f) {
                 int l = this.nodeEvaluator.getNeighbors(this.neighbors, pathpoint1);
 
                 for (int i1 = 0; i1 < l; ++i1) {
@@ -90,10 +94,10 @@ public class PathFinder {
                     pathpoint2.walkedDistance = pathpoint1.walkedDistance + f2;
                     float f3 = pathpoint1.g + f2 + pathpoint2.costMalus;
 
-                    if (pathpoint2.walkedDistance < followRange && (!pathpoint2.inOpenSet() || f3 < pathpoint2.g)) {
+                    if (pathpoint2.walkedDistance < f && (!pathpoint2.inOpenSet() || f3 < pathpoint2.g)) {
                         pathpoint2.cameFrom = pathpoint1;
                         pathpoint2.g = f3;
-                        pathpoint2.h = this.getBestH(pathpoint2, set) * 1.5F;
+                        pathpoint2.h = this.a(pathpoint2, list) * 1.5F; // Paper - list instead of set
                         if (pathpoint2.inOpenSet()) {
                             this.openSet.a(pathpoint2, pathpoint2.g + pathpoint2.h);
                         } else {
@@ -105,31 +109,32 @@ public class PathFinder {
             }
         }
 
-        Optional<Path> optional = !set2.isEmpty() ? set2.stream().map((pathdestination1) -> {
-            return this.reconstructPath(pathdestination1.getBestNode(), (BlockPos) positions.get(pathdestination1), true);
-        }).min(Comparator.comparingInt(Path::getNodeCount)) : set.stream().map((pathdestination1) -> {
-            return this.reconstructPath(pathdestination1.getBestNode(), (BlockPos) positions.get(pathdestination1), false);
-        }).min(Comparator.comparingDouble(Path::getDistToTarget).thenComparingInt(Path::getNodeCount));
-
-        if (!optional.isPresent()) {
-            return null;
-        } else {
-            Path pathentity = (Path) optional.get();
-
-            return pathentity;
+        // Paper start - remove streams - and optimize collection
+        Path best = null;
+        boolean useSet1 = set2.isEmpty();
+        Comparator<Path> comparator = useSet1 ? Comparator.comparingInt(Path::getNodeCount)
+            : Comparator.comparingDouble(Path::getDistToTarget).thenComparingInt(Path::getNodeCount);
+        for (Map.Entry<Target, BlockPos> entry : useSet1 ? list : set2) {
+            Path pathEntity = this.reconstructPath(entry.getKey().getBestNode(), entry.getValue(), !useSet1);
+            if (best == null || comparator.compare(pathEntity, best) < 0)
+                best = pathEntity;
         }
+        return best;
+        // Paper end
     }
 
-    private float getBestH(Node node, Set<Target> targets) {
+    private float a(Node pathpoint, List<Map.Entry<Target, BlockPos>> list) { // Paper - optimize collection
         float f = Float.MAX_VALUE;
 
         float f1;
 
-        for (Iterator iterator = targets.iterator(); iterator.hasNext(); f = Math.min(f1, f)) {
-            Target pathdestination = (Target) iterator.next();
+        // Paper start - optimize collection
+        for (int i = 0, listSize = list.size(); i < listSize; f = Math.min(f1, f), i++) { // Paper
+            Target pathdestination = list.get(i).getKey(); // Paper
+            // Paper end
 
-            f1 = node.distanceTo(pathdestination);
-            pathdestination.updateBest(f1, node);
+            f1 = pathpoint.distanceTo(pathdestination);
+            pathdestination.updateBest(f1, pathpoint);
         }
 
         return f;