From 12806bd94f30695da351d90cc569f5b5ca3863a9 Mon Sep 17 00:00:00 2001
From: Paul Gessinger <hello@paulgessinger.com>
Date: Wed, 11 Dec 2024 16:23:42 +0100
Subject: [PATCH 1/2] fix: Optimize EDM4hep particle reading

---
 Examples/Io/EDM4hep/src/EDM4hepReader.cpp | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/Examples/Io/EDM4hep/src/EDM4hepReader.cpp b/Examples/Io/EDM4hep/src/EDM4hepReader.cpp
index 0be54783e8e..957593ceb32 100644
--- a/Examples/Io/EDM4hep/src/EDM4hepReader.cpp
+++ b/Examples/Io/EDM4hep/src/EDM4hepReader.cpp
@@ -241,10 +241,10 @@ ProcessCode EDM4hepReader::read(const AlgorithmContext& ctx) {
 
   ACTS_DEBUG("Found " << unorderedParticlesInitial.size() << " particles");
 
-  // @TODO: Order simhits by time
-
-  SimParticleContainer particlesGenerator;
-  SimParticleContainer particlesSimulated;
+  std::vector<SimParticle> particlesGeneratorUnordered;
+  particlesGeneratorUnordered.reserve(mcParticleCollection.size());
+  std::vector<SimParticle> particlesSimulatedUnordered;
+  particlesSimulatedUnordered.reserve(mcParticleCollection.size());
 
   for (const auto& inParticle : mcParticleCollection) {
     auto particleIt = edm4hepParticleMap.find(inParticle.getObjectID().index);
@@ -256,7 +256,7 @@ ProcessCode EDM4hepReader::read(const AlgorithmContext& ctx) {
     const std::size_t index = particleIt->second;
     const auto& particleInitial = unorderedParticlesInitial.at(index);
     if (!inParticle.isCreatedInSimulation()) {
-      particlesGenerator.insert(particleInitial);
+      particlesGeneratorUnordered.push_back(particleInitial);
     }
     SimParticle particleSimulated = particleInitial;
 
@@ -286,9 +286,17 @@ ProcessCode EDM4hepReader::read(const AlgorithmContext& ctx) {
                  << particleInitial.fourMomentum().transpose() << " -> "
                  << particleSimulated.final().fourMomentum().transpose());
 
-    particlesSimulated.insert(particleSimulated);
+    particlesSimulatedUnordered.push_back(particleSimulated);
   }
 
+  std::ranges::sort(particlesGeneratorUnordered, detail ::CompareParticleId{});
+  std::ranges::sort(particlesSimulatedUnordered, detail ::CompareParticleId{});
+
+  SimParticleContainer particlesGenerator{particlesGeneratorUnordered.begin(),
+                                          particlesGeneratorUnordered.end()};
+  SimParticleContainer particlesSimulated{particlesSimulatedUnordered.begin(),
+                                          particlesSimulatedUnordered.end()};
+
   if (!m_cfg.graphvizOutput.empty()) {
     std::string path = perEventFilepath(m_cfg.graphvizOutput, "particles.dot",
                                         ctx.eventNumber);

From 2b9db42fb5ab98818ecd415bf2815ae13ff65512 Mon Sep 17 00:00:00 2001
From: Paul Gessinger <hello@paulgessinger.com>
Date: Wed, 11 Dec 2024 16:36:08 +0100
Subject: [PATCH 2/2] also insert simhits in one go

---
 Examples/Io/EDM4hep/src/EDM4hepReader.cpp | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/Examples/Io/EDM4hep/src/EDM4hepReader.cpp b/Examples/Io/EDM4hep/src/EDM4hepReader.cpp
index 957593ceb32..1562105d338 100644
--- a/Examples/Io/EDM4hep/src/EDM4hepReader.cpp
+++ b/Examples/Io/EDM4hep/src/EDM4hepReader.cpp
@@ -12,6 +12,7 @@
 #include "Acts/Plugins/DD4hep/DD4hepDetectorElement.hpp"
 #include "Acts/Plugins/EDM4hep/EDM4hepUtil.hpp"
 #include "ActsExamples/DD4hepDetector/DD4hepDetector.hpp"
+#include "ActsExamples/EventData/GeometryContainers.hpp"
 #include "ActsExamples/EventData/SimHit.hpp"
 #include "ActsExamples/EventData/SimParticle.hpp"
 #include "ActsExamples/Framework/WhiteBoard.hpp"
@@ -304,13 +305,15 @@ ProcessCode EDM4hepReader::read(const AlgorithmContext& ctx) {
     graphviz(dot, unorderedParticlesInitial, parentRelationship);
   }
 
-  SimHitContainer simHits;
+  std::vector<SimHit> simHitsUnordered;
 
   ACTS_DEBUG("Reading sim hits from " << m_cfg.inputSimHits.size()
                                       << " sim hit collections");
   for (const auto& name : m_cfg.inputSimHits) {
     const auto& inputHits = frame.get<edm4hep::SimTrackerHitCollection>(name);
 
+    simHitsUnordered.reserve(simHitsUnordered.size() + inputHits.size());
+
     for (const auto& hit : inputHits) {
       auto simHit = EDM4hepUtil::readSimHit(
           hit,
@@ -367,10 +370,14 @@ ProcessCode EDM4hepReader::read(const AlgorithmContext& ctx) {
             return surface->geometryId();
           });
 
-      simHits.insert(std::move(simHit));
+      simHitsUnordered.push_back(std::move(simHit));
     }
   }
 
+  std::ranges::sort(simHitsUnordered, detail ::CompareGeometryId{});
+
+  SimHitContainer simHits{simHitsUnordered.begin(), simHitsUnordered.end()};
+
   if (m_cfg.sortSimHitsInTime) {
     ACTS_DEBUG("Sorting sim hits in time");
     std::multimap<ActsFatras::Barcode, std::size_t> hitsByParticle;