operatorinfo.h

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//
// Created by Florian Bischoff on 11/2/23.
//
 
#ifndef MADNESS_OPERATORINFO_H
#define MADNESS_OPERATORINFO_H
 
namespace madness {
 
/// operator types
enum OpType {
    OT_UNDEFINED,
    OT_ONE,         /// indicates the identity
    OT_G12,         /// 1/r
    OT_SLATER,      /// exp(-r)
    OT_GAUSS,       /// exp(-r2)
    OT_F12,         /// 1-exp(-r)
    OT_FG12,        /// (1-exp(-r))/r
    OT_F212,        /// (1-exp(-r))^2
    OT_F2G12,       /// (1-exp(-r))^2/r = 1/r + exp(-2r)/r - 2 exp(-r)/r
    OT_BSH,         /// exp(-r)/r
    OT_SIZE         /// for ending loops
};
 
/// operator type to string
template<std::size_t N=1>   // dummy template argument to avoid ambiguity with the other operator<<
std::ostream& operator<<(std::ostream& os, const OpType type) {
    auto name = [](OpType type) {
        switch (type) {
            case OpType::OT_UNDEFINED:
                return "undefined";
            case OpType::OT_ONE:
                return "identity";
            case OpType::OT_G12:
                return "g12";
            case OpType::OT_SLATER:
                return "slater";
            case OpType::OT_GAUSS:
                return "gauss";
            case OpType::OT_F12:
                return "f12";
            case OpType::OT_FG12:
                return "fg12";
            case OpType::OT_F212:
                return "f12^2";
            case OpType::OT_F2G12:
                return "f12^2g";
            case OpType::OT_BSH:
                return "bsh";
            default:
                return "undefined";
        }
    };
    os << name(type);
    return os;
}
 
struct OperatorInfo {
    OperatorInfo() = default;
    OperatorInfo(double mu, double lo, double thresh, OpType type, std::optional<bool> truncate = {}, std::vector<KernelRange> range = std::vector<KernelRange>(6)) : mu(mu), lo(lo), thresh(thresh), type(type), truncate_lowexp_gaussians(truncate), range(std::move(range)) { }
    template <std::size_t NDIM>
    OperatorInfo(double mu, double lo, double thresh, OpType type, std::optional<bool> truncate, const std::array<KernelRange, NDIM>& range) : mu(mu), lo(lo), thresh(thresh), type(type), truncate_lowexp_gaussians(truncate), range(range.begin(), range.end()) { }
    double mu=0.0;     ///< some introspection
    double lo=1.e-5;
    double thresh=1.e-4;
    OpType type=OT_UNDEFINED;    ///< introspection
    double hi=-1.0;
    std::vector<KernelRange> range = std::vector<KernelRange>(6);
    bool debug=false;
    std::optional<bool> truncate_lowexp_gaussians;  // if given, overrides the default for whether to truncate low-exponent gaussians
 
    template <std::size_t NDIM>
    std::array<KernelRange, NDIM> range_as_array() const {
      std::array<KernelRange, NDIM> result;
      MADNESS_ASSERT(range.size() >= NDIM);
      std::copy(range.begin(), range.begin()+NDIM, result.begin());
      return result;
    }
};
 
 
 
}
#endif //MADNESS_OPERATORINFO_H