utils.hpp

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// Copyright (c) 2021 Simons Foundation
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You may obtain a copy of the License at
//     https://www.gnu.org/licenses/gpl-3.0.txt
//
// Authors: Philipp Dumitrescu, Nils Wentzell

 
#pragma once
 
#include "./concepts.hpp"
 
#include <nda/nda.hpp>
 
#include <limits>
#include <type_traits>
#include <utility>
 
namespace triqs::stat {


  template <typename T> [[nodiscard]] auto make_real(T &&t) { return nda::make_regular(nda::real(std::forward<T>(t))); }

  template <typename T> using get_real_t = std::remove_cvref_t<decltype(make_real(std::declval<T>()))>;

  template <typename T> using get_regular_t = std::remove_cvref_t<decltype(nda::make_regular(std::declval<T>()))>;

  template <StatCompatible T> [[nodiscard]] auto zeroed_sample([[maybe_unused]] T const &sample) {
    if constexpr (nda::Scalar<T>) {
      return T{0};
    } else {
      return get_regular_t<T>::zeros(sample.shape());
    }
  }

  template <StatCompatible T> [[nodiscard]] auto nan_sample([[maybe_unused]] T const &sample) {
    if constexpr (nda::Scalar<T>) {
      using real_t = std::remove_cvref_t<decltype(std::real(std::declval<T>()))>;
      return T{std::numeric_limits<real_t>::quiet_NaN()};
    } else {
      using elem_t      = typename get_regular_t<T>::value_type;
      using real_elem_t = std::remove_cvref_t<decltype(std::real(std::declval<elem_t>()))>;
      auto res          = get_regular_t<T>(sample.shape());
      res()             = elem_t{std::numeric_limits<real_elem_t>::quiet_NaN()};
      return res;
    }
  }

  [[nodiscard]] auto abs_square(auto const &x) { return make_real(nda::hadamard(nda::conj(x), x)); }

 
} // namespace triqs::stat