PaperMC/patches/server/0548-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

1.17 Update: Please do this k thx bb
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 076f2dea0e75577ccb0316b3171ed8f44ab6d2ba..3dc896a7ded8d5d109100a393c8299e308954d99 100644
--- a/src/main/java/net/minecraft/world/level/pathfinder/PathFinder.java
+++ b/src/main/java/net/minecraft/world/level/pathfinder/PathFinder.java
@@ -35,27 +35,31 @@ public class PathFinder {
         this.openSet.clear();
         this.nodeEvaluator.prepare(world, mob);
         Node node = this.nodeEvaluator.getStart();
-        Map<Target, BlockPos> map = positions.stream().collect(Collectors.toMap((blockPos) -> {
-            return this.nodeEvaluator.getGoal((double)blockPos.getX(), (double)blockPos.getY(), (double)blockPos.getZ());
-        }, Function.identity()));
+        // Paper start - remove streams - and optimize collection
+        List<Map.Entry<Target, BlockPos>> map = Lists.newArrayList();
+        for (BlockPos blockPos : positions) {
+            map.add(new java.util.AbstractMap.SimpleEntry<>(this.nodeEvaluator.getGoal(blockPos.getX(), blockPos.getY(), blockPos.getZ()), blockPos));
+        }
+        // Paper end
         Path path = this.findPath(world.getProfiler(), node, map, followRange, distance, rangeMultiplier);
         this.nodeEvaluator.done();
         return path;
     }
 
     @Nullable
-    private Path findPath(ProfilerFiller profiler, Node startNode, Map<Target, BlockPos> positions, float followRange, int distance, float rangeMultiplier) {
+    // Paper start - optimize collection
+    private Path findPath(ProfilerFiller profiler, Node startNode, List<Map.Entry<Target, BlockPos>> positions, float followRange, int distance, float rangeMultiplier) {
         profiler.push("find_path");
         profiler.markForCharting(MetricCategory.PATH_FINDING);
-        Set<Target> set = positions.keySet();
+        //Set<Target> set = positions.keySet();
         startNode.g = 0.0F;
-        startNode.h = this.getBestH(startNode, set);
+        startNode.h = this.getBestH(startNode, positions); // Paper - optimize collection
         startNode.f = startNode.h;
         this.openSet.clear();
         this.openSet.insert(startNode);
-        Set<Node> set2 = ImmutableSet.of();
+        //Set<Node> set2 = ImmutableSet.of(); // Paper - unused - diff on change
         int i = 0;
-        Set<Target> set3 = Sets.newHashSetWithExpectedSize(set.size());
+        List<Map.Entry<Target, BlockPos>> entryList = Lists.newArrayListWithExpectedSize(positions.size()); // Paper - optimize collection
         int j = (int)((float)this.maxVisitedNodes * rangeMultiplier);
 
         while(!this.openSet.isEmpty()) {
@@ -67,14 +71,18 @@ public class PathFinder {
             Node node = this.openSet.pop();
             node.closed = true;
 
-            for(Target target : set) {
+            // Paper start - optimize collection
+            for(int i1 = 0; i1 < positions.size(); i1++) {
+                final Map.Entry<Target, BlockPos> entry = positions.get(i1);
+                Target target = entry.getKey();
                 if (node.distanceManhattan(target) <= (float)distance) {
                     target.setReached();
-                    set3.add(target);
+                    entryList.add(entry);
+                    // Paper end
                 }
             }
 
-            if (!set3.isEmpty()) {
+            if (!entryList.isEmpty()) { // Paper - rename variable
                 break;
             }
 
@@ -89,7 +97,7 @@ public class PathFinder {
                     if (node2.walkedDistance < followRange && (!node2.inOpenSet() || g < node2.g)) {
                         node2.cameFrom = node;
                         node2.g = g;
-                        node2.h = this.getBestH(node2, set) * 1.5F;
+                        node2.h = this.getBestH(node2, positions) * 1.5F; // Paper - list instead of set
                         if (node2.inOpenSet()) {
                             this.openSet.changeCost(node2, node2.g + node2.h);
                         } else {
@@ -101,19 +109,27 @@ public class PathFinder {
             }
         }
 
-        Optional<Path> optional = !set3.isEmpty() ? set3.stream().map((target) -> {
-            return this.reconstructPath(target.getBestNode(), positions.get(target), true);
-        }).min(Comparator.comparingInt(Path::getNodeCount)) : set.stream().map((target) -> {
-            return this.reconstructPath(target.getBestNode(), positions.get(target), false);
-        }).min(Comparator.comparingDouble(Path::getDistToTarget).thenComparingInt(Path::getNodeCount));
-        profiler.pop();
-        return !optional.isPresent() ? null : optional.get();
+        // Paper start - remove streams - and optimize collection
+        Path best = null;
+        boolean entryListIsEmpty = entryList.isEmpty();
+        Comparator<Path> comparator = entryListIsEmpty ? Comparator.comparingInt(Path::getNodeCount)
+            : Comparator.comparingDouble(Path::getDistToTarget).thenComparingInt(Path::getNodeCount);
+        for (Map.Entry<Target, BlockPos> entry : entryListIsEmpty ? positions : entryList) {
+            Path path = this.reconstructPath(entry.getKey().getBestNode(), entry.getValue(), !entryListIsEmpty);
+            if (best == null || comparator.compare(path, best) < 0)
+                best = path;
+        }
+        return best;
+        // Paper end
     }
 
-    private float getBestH(Node node, Set<Target> targets) {
+    private float getBestH(Node node, List<Map.Entry<Target, BlockPos>> targets) { // Paper - optimize collection - Set<Target> -> List<Map.Entry<Target, BlockPos>>
         float f = Float.MAX_VALUE;
 
-        for(Target target : targets) {
+        // Paper start - optimize collection
+        for (int i = 0, targetsSize = targets.size(); i < targetsSize; i++) {
+            final Target target = targets.get(i).getKey();
+            // Paper end
             float g = node.distanceTo(target);
             target.updateBest(g, node);
             f = Math.min(g, f);