real_gaunt_table.h

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#ifndef REAL_GAUNT_TABLE_H_
#define REAL_GAUNT_TABLE_H_
 
#include <array>
#include <map>
 
#include <ATen/tensor.h>
 
class RealGauntTable
{
  public:
    RealGauntTable(RealGauntTable const&) = delete;
    RealGauntTable& operator=(RealGauntTable const&) = delete;
 
    ~RealGauntTable() {}
 
    static RealGauntTable& instance()
    {
        static RealGauntTable instance_;
        return instance_;
    }
 
    void build(const int lmax);
 
    const double& operator()(const int l1, const int l2, const int l3, const int m1, const int m2, const int m3) const;
 
    int lmax() const { return lmax_; }
 
    size_t memory() const
    {
        return gaunt_table_.size() * (6 * sizeof(int) + sizeof(double)) 
                + real_gaunt_table_.NumElements() * sizeof(double);
    }
 
 
    double gaunt(const int l1, const int l2, const int l3, const int m1, const int m2, const int m3) const;
 
 
  private:
    RealGauntTable() {}
 
    int lmax_ = -1;
 
    std::map<std::array<int, 6>, double> gaunt_table_;
 
    container::Tensor real_gaunt_table_{container::DataType::DT_DOUBLE, container::TensorShape({0})};
 
    bool gaunt_select_l(const int l1, const int l2, const int l3) const;
 
    bool gaunt_select_m(const int m1, const int m2, const int m3) const { return m1 + m2 + m3 == 0; }
 
    bool real_gaunt_select_m(const int m1, const int m2, const int m3) const;
 
    bool is_valid_lm(const int l1, const int l2, const int l3, const int m1, const int m2, const int m3) const;
 
    double gaunt_lookup(const int l1, const int l2, const int l3, const int m1, const int m2, const int m3) const;
 
    double real_gaunt_lookup(const int l1, const int l2, const int l3, const int m1, const int m2, const int m3) const;
 
    std::array<int, 6> gaunt_key(const int l1, const int l2, const int l3, const int m1, const int m2, const int m3) const;
 
    void arrange(int& l1, int& l2, int& m1, int& m2) const;
 
    double factorial(const int n) const;
 
    int index_map(int l, int m) const;
 
    int minus_1_pow(int m) const { return m % 2 ? -1 : 1; }
};
 
#endif