insert.cpp

// Copyright (c) 2017--present, The Simons Foundation
// This file is part of TRIQS/ctint 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.
 
#include "./insert.hpp"
 
namespace triqs_ctint::moves {
 
  mc_weight_t insert::attempt() {
    TRIQS_ASSERT(n_insertions > 0);
 
    auto single_insert = [&]() {
      // Pick up one factory at random
      int n_fact       = vertex_factories.size();
      auto const &fact = vertex_factories[rng(n_fact)];
 
      // Generate a vertex from the factory
      vertex_t v = fact();
 
      // Lazy add the vertex to the det
      lazy_op << v;
 
      // Calculate Monte-Carlo weight
      double insert_proposition_proba = v.proposition_proba / n_fact;
      U_scalar_t weight               = v.amplitude / insert_proposition_proba;
 
      // Move new vertex to its storage
      qmc_config->vertex_lst.push_back(std::move(v));
 
      return weight;
    };
 
    // Lazy insert and capture the weight for the vertices
    U_scalar_t ratio = 1;
    for (int i = 0; i < n_insertions; ++i) { ratio *= single_insert(); }
 
    // Execute the insertion move
    g_tau_scalar_t const det_ratio = lazy_op.execute_try_insert();
 
    // Calculate the removal proposition probability
    double remove_proposition_proba = 0.0;
    if (max_order == -1 || qmc_config->perturbation_order() < max_order) {
      remove_proposition_proba = 1.0 / std::pow(qmc_config->perturbation_order(), n_insertions);
    }
 
    // Return the overall weight
    return mc_weight_t{det_ratio} * remove_proposition_proba * ratio;
  }
 
  mc_weight_t insert::accept() {
    for (auto &d : qmc_config->dets) d.complete_operation(); // maybe doing nothing if not try_insert but it is quick
    return 1.0;                                              // no need for a correction of the sign
  }
 
  void insert::reject() {
    for (int i = 0; i < n_insertions; ++i) qmc_config->vertex_lst.pop_back(); // remove the last insertions.
    for (auto &d : qmc_config->dets) d.reject_last_try();                     // reject the last try in all determinants
  }
 
} // namespace triqs_ctint::moves