[PWGLF] Avoid pair repeat in mixing

PWGLF/Tasks/Strangeness/lambdaspincorrderived.cxx

@@ -1,4 +1,4 @@
 // Copyright 2019-2020 CERN and copyright holders of ALICE O2.
 // See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
 // All rights not expressly granted are reserved.
 //
@@ -12,7 +12,7 @@
 /// \file taskLambdaSpinCorr.cxx
 /// \brief Analysis task for Lambda spin spin correlation
 ///
 /// \author sourav.kundu@cern.ch
 
 #include "PWGLF/DataModel/LFSpincorrelationTables.h"
 
@@ -29,12 +29,12 @@
 #include <Math/GenVector/Boost.h>
 #include <Math/Vector3D.h>
 #include <Math/Vector4D.h>
 #include <TLorentzVector.h>
 #include <TMath.h>
 
 #include <fairlogger/Logger.h>
 
 #include <iostream>
 #include <iterator>
 #include <string>
 #include <vector>
@@ -44,7 +44,7 @@
 using namespace o2::framework::expressions;
 using namespace o2::soa;
 
 struct lambdaspincorrderived {
   // event sel/////////
   Configurable<float> centMin{"centMin", 0, "Minimum Centrality"};
   Configurable<float> centMax{"centMax", 80, "Maximum Centrality"};
@@ -64,8 +64,8 @@
 
   // Event Mixing
   Configurable<int> nEvtMixing{"nEvtMixing", 10, "Number of events to mix"};
   ConfigurableAxis CfgVtxBins{"CfgVtxBins", {10, -10, 10}, "Mixing bins - z-vertex"};
   ConfigurableAxis CfgMultBins{"CfgMultBins", {8, 0.0, 80}, "Mixing bins - centrality"};
   Configurable<float> etaMix{"etaMix", 0.1, "Eta cut on event mixing"};
   Configurable<float> ptMix{"ptMix", 0.1, "Pt cut on event mixing"};
   Configurable<float> phiMix{"phiMix", 0.1, "Phi cut on event mixing"};
@@ -181,7 +181,7 @@
     cosThetaDiff = proton1LambdaRF.Vect().Unit().Dot(proton2LambdaRF.Vect().Unit());
     double deltaPhi = RecoDecay::constrainAngle(particle1Dummy.Phi() - particle2Dummy.Phi(), 0.0F, 2U);
     double deltaEta = particle1Dummy.Eta() - particle2Dummy.Eta();
     double deltaR = TMath::Sqrt(deltaEta * deltaEta + deltaPhi * deltaPhi);
 
     if (datatype == 0) {
       if (tag1 == 0 && tag2 == 0) {
@@ -259,14 +259,23 @@
   Preslice<aod::LambdaPairs> tracksPerCollisionV0 = aod::lambdapair::lambdaeventId;
   void processME(EventCandidates const& collisions, AllTrackCandidates const& V0s)
   {
+    auto collOldIndex = -999;
+    std::vector<bool> t1Used;
     for (auto& [collision1, collision2] : selfCombinations(colBinning, nEvtMixing, -1, collisions, collisions)) {
       // LOGF(info, "Mixed event collisions: (%d, %d)", collision1.index(), collision2.index());
       auto centrality = collision1.cent();
       auto groupV01 = V0s.sliceBy(tracksPerCollisionV0, collision1.globalIndex());
       auto groupV02 = V0s.sliceBy(tracksPerCollisionV0, collision1.globalIndex());
       auto groupV03 = V0s.sliceBy(tracksPerCollisionV0, collision2.globalIndex());
-      std::vector<bool> t1Used(groupV01.size(), false); // <-- reset here
+      auto collNewIndex = collision1.index();
+      // LOGF(info, "Mixed event collisions: (%d, %d)", collNewIndex, collOldIndex);
+      if (collOldIndex != collNewIndex) {
+        t1Used.resize(groupV01.size(), false);
+        // std::fill(t1Used.begin(), t1Used.end(), false);
+        // std::vector<bool> t1Used(groupV01.size(), false); // <-- reset here
+        collOldIndex = collNewIndex;
+      }
       for (auto& [t1, t3] : soa::combinations(o2::soa::CombinationsFullIndexPolicy(groupV01, groupV03))) {
         if (t1Used[t1.index()]) {
           continue;
         }