Program Listing for File integral_functions.hpp

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//
// Created by Zack Williams on 27/11/2020.
//

#ifndef UW12_INTEGRAL_FUNCTIONS_HPP
#define UW12_INTEGRAL_FUNCTIONS_HPP

#include <functional>
#include <vector>

#include "utils/linalg.hpp"
#include "utils/parallel.hpp"

namespace uw12::integrals {
using TwoIndexFn = std::function<linalg::Mat()>;

using ThreeIndexFn = std::function<linalg::Mat(size_t)>;

inline linalg::Mat coulomb_3idx(
    const ThreeIndexFn &three_index_fn,
    const std::vector<size_t> &df_offsets,
    const size_t n_rows,
    const size_t n_df
) {
  linalg::Mat result(n_rows, n_df);

  const auto n_df_sh = df_offsets.size();

  const auto parallel_fn =
      [&result, &three_index_fn, &df_offsets](const size_t A) {
        const auto off_a = df_offsets[A];

        const auto shell_results = three_index_fn(A);

        linalg::assign_cols(result, shell_results, off_a);
      };

  parallel::parallel_for(0, n_df_sh, parallel_fn);

  return result;
}
}  // namespace uw12::integrals

#endif  // UW12_INTEGRAL_FUNCTIONS_HPP