From 9eee2e80263479fc4f0b7bb89cf60857aaa04ac1 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Fri, 3 Jul 2026 02:28:06 +0000
Subject: [PATCH] =?UTF-8?q?=E2=9A=A1=20Bolt:=20Eliminate=20hot=20path=20LI?=
 =?UTF-8?q?NQ=20allocations=20in=20RobotMerger?=
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Co-authored-by: lordhippo <5122916+lordhippo@users.noreply.github.com>
---
 Vision/Tracking/RobotMerger.cs | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/Vision/Tracking/RobotMerger.cs b/Vision/Tracking/RobotMerger.cs
index b217fb73..67067958 100644
--- a/Vision/Tracking/RobotMerger.cs
+++ b/Vision/Tracking/RobotMerger.cs
@@ -1,5 +1,6 @@
 using System.Numerics;
 using Tyr.Common.Config;
+using Tyr.Common.Data;
 using Tyr.Common.Data.Ssl;
 using Tyr.Common.Math;
 using Tyr.Common.Vision.Data;
@@ -13,17 +14,34 @@ public partial class RobotMerger
         "Factor to weight stdDeviation during tracker merging, reasonable range: 1.0 - 2.0. High values lead to more jitter")]
     private static float MergePower { get; set; } = 1.5f;
 
+    // Bolt: eliminates ~150 allocs/sec (SelectMany, GroupBy, ToDictionary, and inner lists) at 100Hz
+    private readonly Dictionary<RobotId, List<RobotTracker>> _trackersById = new(CommonConfigs.MaxRobots * 2);
+
     public List<FilteredRobot> Process(IEnumerable<Camera> cameras, Timestamp timestamp)
     {
-        var trackersById = cameras
-            .SelectMany(camera => camera.Robots.Values)
-            .GroupBy(robot => robot.Id)
-            .ToDictionary(grouping => grouping.Key, grouping => grouping.ToList());
+        foreach (var list in _trackersById.Values)
+        {
+            list.Clear();
+        }
+
+        foreach (var camera in cameras)
+        {
+            foreach (var tracker in camera.Robots.Values)
+            {
+                if (!_trackersById.TryGetValue(tracker.Id, out var list))
+                {
+                    list = new List<RobotTracker>(4);
+                    _trackersById[tracker.Id] = list;
+                }
+                list.Add(tracker);
+            }
+        }
 
-        var mergedRobots = new List<FilteredRobot>();
+        var mergedRobots = new List<FilteredRobot>(_trackersById.Count);
 
-        foreach (var (id, trackers) in trackersById)
+        foreach (var (id, trackers) in _trackersById)
         {
+            if (trackers.Count == 0) continue;
             mergedRobots.Add(Merge(id, trackers, timestamp));
         }