From 9c986702fd6e6abe988260432be4ef6d26d00d87 Mon Sep 17 00:00:00 2001
From: shahoian <ruben.shahoyan@cern.ch>
Date: Tue, 19 Oct 2021 19:05:11 +0200
Subject: [PATCH] Fix C/A beam assignment (0,1) and P2 offsets

---
 .../Constants/include/CommonConstants/LHCConstants.h | 10 ++++++----
 .../common/include/CommonDataFormat/BunchFilling.h   | 12 ++++++------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/Common/Constants/include/CommonConstants/LHCConstants.h b/Common/Constants/include/CommonConstants/LHCConstants.h
index f831c111da634..358136b77e2d8 100644
--- a/Common/Constants/include/CommonConstants/LHCConstants.h
+++ b/Common/Constants/include/CommonConstants/LHCConstants.h
@@ -23,9 +23,11 @@ namespace constants
 namespace lhc
 {
 // LHC Beam1 and Beam2 definitions
-enum BeamDirection : int { BeamClockWise,
-                           BeamAntiClockWise,
-                           NBeamDirections };
+enum BeamDirection : int { BeamClockWise,     // beamC = beam 1,
+                           BeamAntiClockWise, // beamA = beam 2
+                           NBeamDirections,
+                           InteractingBC = -1 // as used in the BunchFilling class
+};
 constexpr int LHCMaxBunches = 3564;                              // max N bunches
 constexpr double LHCRFFreq = 400.789e6;                          // LHC RF frequency in Hz
 constexpr double LHCBunchSpacingNS = 10 * 1.e9 / LHCRFFreq;      // bunch spacing in ns (10 RFbuckets)
@@ -36,7 +38,7 @@ constexpr double LHCOrbitMUS = LHCOrbitNS * 1e-3;                // orbit durati
 constexpr unsigned int MaxNOrbits = 0xffffffff;
 
 // Offsets of clockwise and anticlockwise beam bunches at P2
-constexpr int BunchOffsetsP2[2] = {346, 3019};
+constexpr int BunchOffsetsP2[2] = {3017, 344};
 
 // convert LHC bunch ID to BC for 2 beam directions
 constexpr int LHCBunch2P2BC(int bunch, BeamDirection dir)
diff --git a/DataFormats/common/include/CommonDataFormat/BunchFilling.h b/DataFormats/common/include/CommonDataFormat/BunchFilling.h
index 077e3cc85b3f4..1fdc1d7ba8443 100644
--- a/DataFormats/common/include/CommonDataFormat/BunchFilling.h
+++ b/DataFormats/common/include/CommonDataFormat/BunchFilling.h
@@ -41,13 +41,13 @@ class BunchFilling
   // get interacting bunches pattern (B)
   const auto& getBCPattern() const { return mPattern; }
 
-  // get pattern or clockwise (0, A) and anticlockwise (1, C) beams at P2
+  // get pattern or clockwise (1, A) and anticlockwise (0, C) beams at P2
   const auto& getBeamPattern(int beam) const { return mBeamAC[beam]; }
 
   // get pattern of interacting BCs (-1) or beams filled BCs at P2 (0,1)
   const auto& getPattern(int dir = -1) const { return dir < 0 ? getBCPattern() : getBeamPattern(dir); }
 
-  // get number of interacting bunches (-1) and number of filled bunches for clockwise (0, A) and anticlockwise (1, C) beams
+  // get number of interacting bunches (-1) and number of filled bunches for clockwise (1, A) and anticlockwise (0, C) beams
   int getNBunches(int dir = -1) const { return dir < 0 ? mPattern.count() : mBeamAC[dir].count(); }
 
   // test interacting bunch
@@ -56,10 +56,10 @@ class BunchFilling
   // test bean bunch
   bool testBeamBunch(int bcID, int dir) const { return mBeamAC[dir][bcID]; }
 
-  // test interacting (-1) or clockwise (0, A) and anticlockwise (1, C) beams bunch
+  // test interacting (-1) or clockwise (1, A) and anticlockwise (0, C) beams bunch
   bool testBC(int bcID, int dir = -1) const { return dir < 0 ? testInteractingBC(bcID) : testBeamBunch(bcID, dir); }
 
-  // BC setters, dir=-1 is for interacting bunches pattern, 0,1 for clockwise (A) and anticlockwise (C) beams
+  // BC setters, dir=-1 is for interacting bunches pattern, 0, 1 for clockwise (C) and anticlockwise (A) beams
   void setBC(int bcID, bool active = true, int dir = -1);
   void setBCTrain(int nBC, int bcSpacing, int firstBC, int dir = -1);
   void setBCTrains(int nTrains, int trainSpacingInBC, int nBC, int bcSpacing, int firstBC, int dir = -1);
@@ -72,7 +72,7 @@ class BunchFilling
   int getFirstFilledBC(int dir = -1) const;
   int getLastFilledBC(int dir = -1) const;
 
-  // print pattern of bunches, dir=0,1: for A,C beams, dir=-1: for interacting BCs, otherwise: all
+  // print pattern of bunches, dir=0,1: for C,A beams, dir=-1: for interacting BCs, otherwise: all
   void print(int dir = -2, int bcPerLine = 100) const;
 
   // set BC filling a la TPC TDR, 12 50ns trains of 48 BCs
@@ -94,7 +94,7 @@ class BunchFilling
   static bool parsePattern(const unsigned char*& input, Pattern& patt, int& ibit, int& level);
 
   Pattern mPattern{};                                                 // Pattern of interacting BCs at P2
-  std::array<Pattern, o2::constants::lhc::NBeamDirections> mBeamAC{}; // pattern of 2 beam bunches at P2
+  std::array<Pattern, o2::constants::lhc::NBeamDirections> mBeamAC{}; // pattern of 2 beam bunches at P2, 0 for C, 1 for A beam
 
   ClassDefNV(BunchFilling, 2);
 };