util.hpp

// Copyright (c) 2022--present, The Simons Foundation
// Copyright (c) 2022--present, Max Planck Institute for Polymer Research, Mainz, Germany
// This file is part of TRIQS/ctseg and is licensed under the terms of GPLv3 or later.
// SPDX-License-Identifier: GPL-3.0-or-later
// See LICENSE in the root of this distribution for details.
 
#pragma once
 
#include <triqs/gfs.hpp>
using namespace triqs::gfs;
 
namespace triqs_ctseg {
 
  inline long modulo(long i, long N) { return (i + N) % N; }
 
  // Same as std::lower_bound, but i-th element of vector is returned by f[i]
  // f is called on 0:N strictly
  long lower_bound(auto f, long N, auto const &value) {
    long first = 0, count = N;
 
    while (count > 0) {
      long step = count / 2;
      assert(first + step < N);
      if (f(first + step) < value) {
        first += step + 1;
        count -= step + 1;
      } else
        count = step;
    }
    return first;
  }
 
  // If we have an ordered det_manip d, we get the lower_bound index for x
  long det_lower_bound_x(auto const &d, auto const &x) {
    return lower_bound([&d](long i) { return d.get_x(i).first; }, d.size(), x);
  }
  long det_lower_bound_y(auto const &d, auto const &y) {
    return lower_bound([&d](long i) { return d.get_y(i).first; }, d.size(), y);
  }
 
  // Integer power
  constexpr unsigned int ipow(unsigned int n, unsigned int m) { return m == 0 ? 1 : m == 1 ? n : n * ipow(n, m - 1); }
 
  // Block2Gf constructor
  template <typename M> block2_gf<M> make_block2_gf(M const &m, gf_struct_t const &gf_struct) {
 
    std::vector<std::vector<gf<M>>> gf_vecvec;
    std::vector<std::string> block_names;
 
    for (auto const &[bl1, bl1_size] : gf_struct) {
      block_names.push_back(bl1);
      std::vector<gf<M>> gf_vec;
      for (auto const &[bl2, bl2_size] : gf_struct) { gf_vec.emplace_back(m, make_shape(bl1_size, bl2_size)); }
      gf_vecvec.emplace_back(std::move(gf_vec));
    }
 
    return make_block2_gf(block_names, block_names, std::move(gf_vecvec));
  }
 
} // namespace triqs_ctseg