From fb2bca56a922abaf31e171cc6bb275607b6d2d09 Mon Sep 17 00:00:00 2001
From: Zuzanna Chochulska <zuzanna.chochulska.stud@pw.edu.pl>
Date: Tue, 14 Nov 2023 13:23:14 +0100
Subject: [PATCH 1/2] Adding swaping to same and mixed events in the MCTruth
 track-track

---
 .../Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx b/PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx
index a7dab8bc872..ae9a39d4ef7 100644
--- a/PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx
+++ b/PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx
@@ -15,6 +15,7 @@
 /// \author Zuzanna Chochulska, WUT Warsaw, zuzanna.chochulska.stud@pw.edu.pl
 
 #include <vector>
+#include <random>
 #include "Framework/AnalysisTask.h"
 #include "Framework/runDataProcessing.h"
 #include "Framework/HistogramRegistry.h"
@@ -169,6 +170,11 @@ struct femtoUniversePairTaskTrackTrackMcTruth {
     }
     /// Now build the combinations
     for (auto& [p1, p2] : combinations(CombinationsStrictlyUpperIndexPolicy(groupPartsOne, groupPartsTwo))) {
+      if (std::rand() > RAND_MAX / 2) {
+        auto& tmp = p1;
+        p1 = p2;
+        p2 = tmp;
+      }
 
       // track cleaning
       if (!pairCleaner.isCleanPair(p1, p2, parts)) {
@@ -208,7 +214,11 @@ struct femtoUniversePairTaskTrackTrackMcTruth {
   {
 
     for (auto& [p1, p2] : combinations(CombinationsFullIndexPolicy(groupPartsOne, groupPartsTwo))) {
-
+      if (std::rand() > RAND_MAX / 2) {
+        auto& tmp = p1;
+        p1 = p2;
+        p2 = tmp;
+      }
       mixedEventCont.setPair<isMC>(p1, p2, multCol, ConfUse3D);
     }
   }

From 8eceab1642aeeda20cbc064f9a2985b2f38f8522 Mon Sep 17 00:00:00 2001
From: Zuzanna Chochulska <zuzanna.chochulska.stud@pw.edu.pl>
Date: Tue, 14 Nov 2023 16:22:21 +0100
Subject: [PATCH 2/2] Add swapping to the MC Truth track track task

---
 ...femtoUniversePairTaskTrackTrackMcTruth.cxx | 32 +++++++++++--------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx b/PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx
index ae9a39d4ef7..96b4bcfbeed 100644
--- a/PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx
+++ b/PWGCF/FemtoUniverse/Tasks/femtoUniversePairTaskTrackTrackMcTruth.cxx
@@ -116,6 +116,9 @@ struct femtoUniversePairTaskTrackTrackMcTruth {
   HistogramRegistry resultRegistry{"Correlations", {}, OutputObjHandlingPolicy::AnalysisObject};
   HistogramRegistry MixQaRegistry{"MixQaRegistry", {}, OutputObjHandlingPolicy::AnalysisObject};
 
+  /// @brief Counter for particle swapping
+  int fNeventsProcessed = 0;
+
   void init(InitContext&)
   {
 
@@ -155,6 +158,8 @@ struct femtoUniversePairTaskTrackTrackMcTruth {
   template <bool isMC, typename PartitionType, typename PartType>
   void doSameEvent(PartitionType groupPartsOne, PartitionType groupPartsTwo, PartType parts, float magFieldTesla, int multCol)
   {
+    bool swpart = fNeventsProcessed % 2;
+    fNeventsProcessed++;
 
     /// Histogramming same event
     for (auto& part : groupPartsOne) {
@@ -170,17 +175,16 @@ struct femtoUniversePairTaskTrackTrackMcTruth {
     }
     /// Now build the combinations
     for (auto& [p1, p2] : combinations(CombinationsStrictlyUpperIndexPolicy(groupPartsOne, groupPartsTwo))) {
-      if (std::rand() > RAND_MAX / 2) {
-        auto& tmp = p1;
-        p1 = p2;
-        p2 = tmp;
-      }
-
       // track cleaning
       if (!pairCleaner.isCleanPair(p1, p2, parts)) {
         continue;
       }
-      sameEventCont.setPair<isMC>(p1, p2, multCol, ConfUse3D);
+      if (swpart)
+        sameEventCont.setPair<isMC>(p1, p2, multCol, ConfUse3D);
+      else
+        sameEventCont.setPair<isMC>(p2, p1, multCol, ConfUse3D);
+
+      swpart = !swpart;
     }
   }
 
@@ -212,14 +216,16 @@ struct femtoUniversePairTaskTrackTrackMcTruth {
   template <bool isMC, typename PartitionType, typename PartType>
   void doMixedEvent(PartitionType groupPartsOne, PartitionType groupPartsTwo, PartType parts, float magFieldTesla, int multCol)
   {
+    bool swpart = fNeventsProcessed % 2;
+    fNeventsProcessed++;
 
     for (auto& [p1, p2] : combinations(CombinationsFullIndexPolicy(groupPartsOne, groupPartsTwo))) {
-      if (std::rand() > RAND_MAX / 2) {
-        auto& tmp = p1;
-        p1 = p2;
-        p2 = tmp;
-      }
-      mixedEventCont.setPair<isMC>(p1, p2, multCol, ConfUse3D);
+      if (swpart)
+        mixedEventCont.setPair<isMC>(p1, p2, multCol, ConfUse3D);
+      else
+        mixedEventCont.setPair<isMC>(p2, p1, multCol, ConfUse3D);
+
+      swpart = !swpart;
     }
   }