BFieldCache.h

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/*
  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
*/

 
#ifndef BFIELDCACHE_H
#define BFIELDCACHE_H
 
#include "CxxUtils/restrict.h"
#include "CxxUtils/vec.h"
#include "MagFieldElements/BFieldVector.h"
 
class BFieldCache
{
public:
  // default constructor sets unphysical boundaries, so that inside() will fail
  BFieldCache() = default;  // cppcheck-suppress uninitMemberVar; m_field uninit on purpose
  // make this cache invalid, so that inside() will fail
  void invalidate();
 
  // set the z, r, phi range that defines the bin
  void setRange(double zmin,
                double zmax,
                double rmin,
                double rmax,
                double phimin,
                double phimax);
 
  // set the 3x8 field array.
  void setField(const CxxUtils::vec<double, 8>& field1,
                const CxxUtils::vec<double, 8>& field2,
                const CxxUtils::vec<double, 8>& field3);
 
  // set the multiplicative factor for the field vectors
  void setBscale(double bscale);
  float bscale() const;
 
  // test if (z, r, phi) is inside this bin
  bool inside(double z, double r, double phi) const;
  // interpolate the field and return B[3].
  // also compute field derivatives if deriv[9] is given.
  void getB(const double* ATH_RESTRICT xyz,
            double r,
            double phi,
            double* ATH_RESTRICT B,
            double* ATH_RESTRICT deriv = nullptr) const;
 
private:
  // bin range in z
  double m_zmin = 0.0;
  double m_zmax = 0.0;
  // bin range in r
  double m_rmin = 0.0;
  double m_rmax = 0.0;
  // bin range in phi
  double m_phimin = 0.0;
  double m_phimax = -1.0;
  // 1/(bin size) in z, r, phi
  double m_invz = 0.0;
  double m_invr = 0.0;
  double m_invphi = 0.0;
  double m_scale = 0.0;             // unit of m_field in kT
  alignas(16) double m_field[3][8]; // (Bz,Br,Bphi) at 8 corners of the bin
};
 
#include "MagFieldElements/BFieldCache.icc"
#endif