BFieldMesh.h

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

//
#ifndef BFIELDMESH_H
#define BFIELDMESH_H
 
#include "CxxUtils/restrict.h"
#include "MagFieldElements/BFieldCache.h"
#include "MagFieldElements/BFieldVector.h"
#include <array>
#include <cmath>
#include <vector>
 
template<class T>
class BFieldMesh
{
public:
  static_assert((std::is_same<T, short>::value ||
                 std::is_same<T, double>::value),
                "Type for the BField Mesh must be one of short or double");
  BFieldMesh() = default;
  BFieldMesh(const BFieldMesh&) = default;
  BFieldMesh(BFieldMesh&&) = default;
  BFieldMesh& operator=(const BFieldMesh&) = default;
  BFieldMesh& operator=(BFieldMesh&&) = default;
  ~BFieldMesh() = default;
  BFieldMesh(double zmin,
             double zmax,
             double rmin,
             double rmax,
             double phimin,
             double phimax,
             double bscale);

  void setRange(double zmin,
                double zmax,
                double rmin,
                double rmax,
                double phimin,
                double phimax);

  void setBscale(double bscale);
  void scaleBscale(double factor);
  void reserve(int nz, int nr, int nphi, int nfield);
  void reserve(int nz, int nr, int nphi);
  void appendMesh(int axis, double value);
  void appendField(const BFieldVector<T>& field);
  void buildLUT();
  /* @brief test if a point is inside this mesh*/
  bool inside(double z, double r, double phi) const;
  /* @brief get the cache corresponding to a particular cell*/
  void getCache(double z,
                double r,
                double phi,
                BFieldCache& cache,
                double scaleFactor = 1.0) const;
  void getB(const double* ATH_RESTRICT xyz,
            double* ATH_RESTRICT B,
            double* ATH_RESTRICT deriv = nullptr) const;
  double min(size_t axis) const;
  double max(size_t axis) const;
  double zmin() const;
  double zmax() const;
  double rmin() const;
  double rmax() const;
  double phimin() const;
  double phimax() const;
  unsigned nmesh(size_t axis) const;
  double mesh(size_t axis, size_t index) const;
  unsigned nfield() const;
  const BFieldVector<T>& field(size_t index) const;
  double bscale() const;
  int memSize() const;
 
protected:
  std::array<double, 3> m_min{};
  std::array<double, 3> m_max{};
  std::array<std::vector<double>, 3> m_mesh{};
 
private:
  std::vector<BFieldVector<T>> m_field;
  double m_scale{1.0};
  double m_nomScale{1.0}; // nominal m_scale from the map
 
  // look-up table and related variables
  std::array<std::vector<int>, 3> m_LUT{};
  std::array<double, 3> m_invUnit{}; // inverse unit size in the LUT
  int m_roff{0};
  int m_zoff{0};
};
#include "MagFieldElements/BFieldMesh.icc"
#endif