From 9ba6e127b845dac1458994426c4a2920da5728f5 Mon Sep 17 00:00:00 2001
From: Paul Gessinger <paul.gessinger@cern.ch>
Date: Sat, 28 Oct 2023 15:23:49 +0200
Subject: [PATCH] fix: CKF does an extra copy on the fitted state (#2568)

---
 Core/include/Acts/TrackFinding/CombinatorialKalmanFilter.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Core/include/Acts/TrackFinding/CombinatorialKalmanFilter.hpp b/Core/include/Acts/TrackFinding/CombinatorialKalmanFilter.hpp
index 30e266bf8b3..49a208547d0 100644
--- a/Core/include/Acts/TrackFinding/CombinatorialKalmanFilter.hpp
+++ b/Core/include/Acts/TrackFinding/CombinatorialKalmanFilter.hpp
@@ -575,7 +575,7 @@ class CombinatorialKalmanFilter {
                   }
                   result.lastError = res.error();
                 } else {
-                  auto fittedState = *res;
+                  const auto& fittedState = *res;
                   // Assign the fitted parameters
                   result.fittedParameters.emplace(
                       result.lastMeasurementIndices.at(result.iSmoothed),