Paper/patches/server/0520-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 300c812d513e0b948a7e79c0ed241f514c7a09fc..d23481453717f715124156b5d83f6448f720d049 100644
--- a/src/main/java/net/minecraft/world/level/pathfinder/PathFinder.java
+++ b/src/main/java/net/minecraft/world/level/pathfinder/PathFinder.java
@@ -38,9 +38,12 @@ public class PathFinder {
         if (node == null) {
             return null;
         } else {
-            Map<Target, BlockPos> map = positions.stream().collect(Collectors.toMap((pos) -> {
-                return this.nodeEvaluator.getGoal((double)pos.getX(), (double)pos.getY(), (double)pos.getZ());
-            }, Function.identity()));
+            // Paper start - remove streams - and optimize collection
+            List<Map.Entry<Target, BlockPos>> map = Lists.newArrayList();
+            for (BlockPos pos : positions) {
+                map.add(new java.util.AbstractMap.SimpleEntry<>(this.nodeEvaluator.getGoal(pos.getX(), pos.getY(), pos.getZ()), pos));
+            }
+            // Paper end
             Path path = this.findPath(world.getProfiler(), node, map, followRange, distance, rangeMultiplier);
             this.nodeEvaluator.done();
             return path;
@@ -48,18 +51,19 @@ public class PathFinder {
     }
 
     @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()) {
@@ -71,14 +75,18 @@ 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;
             }
 
@@ -93,7 +101,7 @@ 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 {
@@ -105,23 +113,31 @@ public class PathFinder {
             }
         }
 
-        Optional<Path> optional = !set3.isEmpty() ? set3.stream().map((node) -> {
-            return this.reconstructPath(node.getBestNode(), positions.get(node), 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
     }
 
     protected float distance(Node a, Node b) {
         return a.distanceTo(b);
     }
 
-    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);