MuonSectorMapping.h

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/*
  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef MUON_MUONSECTORMAPPING_H
#define MUON_MUONSECTORMAPPING_H
 
#include <math.h>
 
#include <array>
#include <iostream>
#include <vector>
 
#include "CxxUtils/checker_macros.h"
 
ATLAS_CHECK_FILE_THREAD_SAFETY;
 
namespace Muon {
 
    class MuonSectorMapping {
    public:
        bool insideSector(int sector, double phi) const;

        int getSector(double phi) const;

        void getSectors(double phi, std::vector<int>& sectors) const;

        double sectorPhi(int sector) const;
        /*** Returns whether the sector is a small sector */
        static bool isSmall(int sector) {
            return sector % 2 == 0;
        }

        double transformPhiToSector(double phi, int sector, bool toSector = true) const;

        double transformRToSector(double r, double phi, int sector, bool toSector = true) const;

        double sectorOverlapPhi(int sector1, int sector2) const;

        bool closeToSectorBoundary(double phi) const;

        double transformRToNeighboringSector(double r, int sectorHit, int sectorTarget) const;

        double sectorSize(int sector) const;

        double sectorWidth(int sector) const;
 
    private:
        static constexpr double s_oneEightsOfPi{M_PI / 8.};                                                 //  pi/8
        static constexpr double s_inverseOneEightsOfPi{8. / M_PI};                                          // 8/pi
        static constexpr std::array<double, 2> s_sectorSize{0.4 * s_oneEightsOfPi, 0.6 * s_oneEightsOfPi};  // side of a sector in radiants
        static constexpr double s_sectorOverlap{0.1 * s_oneEightsOfPi};  // size of the overlap between small and large sectors
        static bool s_debug ATLAS_THREAD_SAFE;                           // if true addition cout is enabled
    };
 
    inline double MuonSectorMapping::sectorSize(int sector) const {
        const int idx = sector % 2;
        return s_sectorSize[idx];
    }
 
    inline double MuonSectorMapping::sectorWidth(int sector) const { return sectorSize(sector) + s_sectorOverlap; }
 
    inline bool MuonSectorMapping::insideSector(int sector, double phi) const {
        double phiInSec = transformPhiToSector(phi, sector);
        if (phiInSec < -sectorWidth(sector)) return false;
        if (phiInSec > sectorWidth(sector)) return false;
        return true;
    }
 
    inline double MuonSectorMapping::sectorPhi(int sector) const {
        if (sector < 10) return M_PI * (sector - 1) / 8.;
        return -M_PI * (2 - (sector - 1) / 8.);
    }
 
    inline int MuonSectorMapping::getSector(double phi) const {
        // remap phi onto sector structure
        double val = (phi + sectorSize(1)) * s_inverseOneEightsOfPi;  // convert to value between -8 and 8, shift by width first sector
        if (val < 0) val += 16;
        int sliceIndex = static_cast<int>(val / 2);  // large/small wedge
        double valueInSlice = val - 2 * sliceIndex;
        int sector = 2 * sliceIndex + 1;
        if (valueInSlice > 1.2) ++sector;
        return sector;
    }
 
    inline void MuonSectorMapping::getSectors(double phi, std::vector<int>& sectors) const {
        int sector = getSector(phi);
        int sectorNext = sector != 16 ? sector + 1 : 1;
        int sectorBefore = sector != 1 ? sector - 1 : 16;
        if (insideSector(sectorBefore, phi)) sectors.push_back(sectorBefore);
        if (insideSector(sector, phi)) sectors.push_back(sector);
        if (insideSector(sectorNext, phi)) sectors.push_back(sectorNext);
    }
 
    inline bool MuonSectorMapping::closeToSectorBoundary(double phi) const {
        std::vector<int> sectors;
        getSectors(phi, sectors);
        return sectors.size() > 1;
    }
 
    inline double MuonSectorMapping::transformPhiToSector(double phi, int sector, bool toSector) const {
        double sign = toSector ? -1 : 1;
        double dphi = phi + sign * sectorPhi(sector);
        if (dphi > M_PI) dphi -= 2 * M_PI;
        if (dphi < -M_PI) dphi += 2 * M_PI;
        return dphi;
    }
 
    inline double MuonSectorMapping::sectorOverlapPhi(int sector1, int sector2) const {
        if (sector1 == sector2) return sectorPhi(sector1);
 
        int s1 = std::min(sector1, sector2);
        int s2 = std::max(sector1, sector2);
        if (s2 == 16 && s1 == 1) {
            s1 = 16;
            s2 = 1;
        } else if (std::abs(s1 - s2) > 1) {
            if (s_debug) std::cout << " bad sector combination: not neighbouring " << s1 << "   " << s2 << std::endl;
            return 0;
        }
 
        double phi1 = sectorPhi(s1);
        double phio1 = phi1 + sectorSize(s1);
        if (phio1 > M_PI) phio1 -= 2 * M_PI;
 
        return phio1;
    }
 
    inline double MuonSectorMapping::transformRToSector(double r, double phi, int sector, bool toSector) const {
        double dphi = transformPhiToSector(phi, sector);
        if (std::abs(dphi) > 0.3 && s_debug) {
            std::cout << " large dphi detected!!: phi " << phi << " sector " << sector << " phi " << sectorPhi(sector) << " " << phi
                      << " dphi " << dphi << std::endl;
        }
        if (toSector)
            return r * std::cos(dphi);
        else
            return r / std::cos(dphi);
    }
 
    inline double MuonSectorMapping::transformRToNeighboringSector(double r, int sectorHit, int sector) const {
        double phi = sectorPhi(sectorHit);
        double phio = sectorOverlapPhi(sectorHit, sector);
        double dphio = phi - phio;
        if (dphio < -M_PI) dphio += 2 * M_PI;
        double redge = r / std::cos(dphio);
        double phi_sec = sectorPhi(sector);
        double dphi = phio - phi_sec;
        if (dphi < -M_PI) dphi += 2 * M_PI;
        if (std::abs(dphi) > 0.3 && s_debug) {
            std::cout << " large dphi detected!!: sector " << sector << " of hit " << sectorHit << " phi ref sector " << phi_sec << " hit "
                      << phi << " dphi " << dphi << std::endl;
        }
        return redge * std::cos(dphi);
    }
 
}  // namespace Muon
 
#endif