transverse_ising.hpp

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//    Copyright 2023 Jij Inc.
 
//    Licensed under the Apache License, Version 2.0 (the "License");
//    you may not use this file except in compliance with the License.
//    You may obtain a copy of the License at
 
//        http://www.apache.org/licenses/LICENSE-2.0
 
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS,
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//    See the License for the specific language governing permissions and
//    limitations under the License.
 
#pragma once
 
#include <cassert>
#include <exception>
#include <vector>
 
#include "openjij/graph/all.hpp"
#include "openjij/system/system.hpp"
#include "openjij/utility/eigen.hpp"
 
namespace openjij {
namespace system {
 
using TrotterSpins = std::vector<graph::Spins>;
 
template <typename GraphType> struct TransverseIsing;
 
template <typename FloatType> struct TransverseIsing<graph::Dense<FloatType>> {
  using system_type = transverse_field_system;
 
  // matrix (row major)
  using MatrixXx =
      Eigen::Matrix<FloatType, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
  // trotter matrix (col major)
  using TrotterMatrix =
      Eigen::Matrix<FloatType, Eigen::Dynamic, Eigen::Dynamic, Eigen::ColMajor>;
 
  TransverseIsing(const TrotterSpins &init_trotter_spins,
                  const graph::Dense<FloatType> &init_interaction,
                  const FloatType gamma)
      : trotter_spins(
            utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
                init_trotter_spins)),
        interaction(init_interaction.get_interactions()),
        num_classical_spins(init_trotter_spins[0].size()), gamma(gamma) {
    if (!(init_trotter_spins.size() >= 2)) {
      throw std::invalid_argument(
          "trotter slices must be equal or larger than 2.");
    }
 
    // initialize rand_pool
    rand_pool = TrotterMatrix(num_classical_spins + 1, trotter_spins.cols());
 
    // reset dE
    reset_dE();
  }
 
  TransverseIsing(const graph::Spins &init_classical_spins,
                  const graph::Dense<FloatType> &init_interaction,
                  const FloatType gamma, const size_t num_trotter_slices)
      : interaction(init_interaction.get_interactions()),
        num_classical_spins(init_classical_spins.size()), gamma(gamma) {
    // initialize trotter_spins with classical_spins
 
    if (!(num_trotter_slices >= 2)) {
      throw std::invalid_argument(
          "trotter slices must be equal or larger than 2.");
    }
 
    TrotterSpins init_trotter_spins(num_trotter_slices);
 
    for (auto &spins : init_trotter_spins) {
      spins = init_classical_spins;
    }
 
    // init trotter_spins
    trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // initialize rand_pool
    rand_pool = TrotterMatrix(num_classical_spins + 1, trotter_spins.cols());
 
    // reset dE
    reset_dE();
  }
 
  void reset_spins(const TrotterSpins &init_trotter_spins) {
    this->trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // reset dE
    reset_dE();
  }
 
  void reset_spins(const graph::Spins &classical_spins) {
    TrotterSpins init_trotter_spins(
        trotter_spins.cols()); // cols -> num_trotter_slices
 
    for (auto &spins : init_trotter_spins) {
      spins = classical_spins;
    }
    // init trotter_spins
    this->trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // reset dE
    reset_dE();
  }
 
  inline void reset_dE() {
    // reset dE and dEtrot
 
    // initialize dE (spatial direction)
    // we store only dE for spatial direction
    const auto &spins = this->trotter_spins;
    // std::size_t num_trotter_slices = this->trotter_spins.cols();
 
    this->dE = -2 * spins.cwiseProduct(this->interaction * spins);
 
    // for trotter direction
    // this->dEtrot = TrotterMatrix::Zero(num_classical_spins+1,
    // num_trotter_slices); for(std::size_t t=0; t<num_trotter_slices; t++){
    //    this->dEtrot.col(t) = -2 * spins.col(t).cwiseProduct(
    //            spins.col(mod_t((int64_t)t+1, num_trotter_slices)) +
    //            spins.col(mod_t((int64_t)t-1, num_trotter_slices))
    //            );
    //}
 
    // diffE = s * (beta/num_trotter_slices) * this->dE + (1/2.) *
    // log(tanh(beta* gamma * (1.0-s) /num_trotter_slices)) * this->dEtrot
  }
 
  inline static std::size_t mod_t(std::int64_t a,
                                  std::size_t num_trotter_slices) {
    // a -> [-1:num_trotter_slices]
    // return a%num_trotter_slices (a>0), num_trotter_slices-1 (a==-1)
    return (a + num_trotter_slices) % num_trotter_slices;
  }
 
  TrotterMatrix trotter_spins;
 
  const MatrixXx interaction;
 
  std::size_t num_classical_spins; // trotter_spins[0].size()-1
 
  FloatType gamma;
 
  TrotterMatrix rand_pool;
 
  TrotterMatrix dE;
};
 
template <typename FloatType> struct TransverseIsing<graph::Sparse<FloatType>> {
  using system_type = transverse_field_system;
 
  // matrix (row major)
  using SparseMatrixXx = Eigen::SparseMatrix<FloatType, Eigen::RowMajor>;
  // trotter matrix (col major)
  using TrotterMatrix =
      Eigen::Matrix<FloatType, Eigen::Dynamic, Eigen::Dynamic, Eigen::ColMajor>;
 
  TransverseIsing(const TrotterSpins &init_trotter_spins,
                  const graph::Sparse<FloatType> &init_interaction,
                  FloatType gamma)
      : trotter_spins(
            utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
                init_trotter_spins)),
        interaction(
            utility::gen_matrix_from_graph<Eigen::RowMajor>(init_interaction)),
        num_classical_spins(init_trotter_spins[0].size()), gamma(gamma) {
    if (!(init_trotter_spins.size() >= 2)) {
      throw std::invalid_argument(
          "trotter slices must be equal or larger than 2.");
    }
 
    // initialize rand_pool
    rand_pool = TrotterMatrix(num_classical_spins + 1, trotter_spins.cols());
 
    // reset dE
    reset_dE();
  }
 
  TransverseIsing(const graph::Spins &init_classical_spins,
                  const graph::Sparse<FloatType> &init_interaction,
                  const FloatType gamma, const size_t num_trotter_slices)
      : interaction(
            utility::gen_matrix_from_graph<Eigen::RowMajor>(init_interaction)),
        num_classical_spins(init_classical_spins.size()), gamma(gamma) {
    // initialize trotter_spins with classical_spins
 
    // assert(init_classical_spins.size() >= 2);
    if (!(num_trotter_slices >= 2)) {
      throw std::invalid_argument(
          "trotter slices must be equal or larger than 2.");
    }
 
    TrotterSpins init_trotter_spins(num_trotter_slices);
 
    for (auto &spins : init_trotter_spins) {
      spins = init_classical_spins;
    }
 
    // init trotter_spins
    trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // initialize rand_pool
    rand_pool = TrotterMatrix(num_classical_spins + 1, trotter_spins.cols());
 
    // reset dE
    reset_dE();
  }
 
  void reset_spins(const TrotterSpins &init_trotter_spins) {
    this->trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // reset dE
    reset_dE();
  }
 
  void reset_spins(const graph::Spins &classical_spins) {
    TrotterSpins init_trotter_spins(
        trotter_spins.cols()); // cols -> num_trotter_slices
 
    for (auto &spins : init_trotter_spins) {
      spins = classical_spins;
    }
    // init trotter_spins
    this->trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // reset dE
    reset_dE();
  }
 
  inline void reset_dE() {
    // reset dE and dEtrot
 
    // initialize dE (spatial direction)
    // we store only dE for spatial direction
    const auto &spins = this->trotter_spins;
    // std::size_t num_trotter_slices = this->trotter_spins.cols();
 
    this->dE = -2 * spins.cwiseProduct(this->interaction * spins);
 
    // for trotter direction
    // this->dEtrot = TrotterMatrix::Zero(num_classical_spins+1,
    // num_trotter_slices); for(std::size_t t=0; t<num_trotter_slices; t++){
    //    this->dEtrot.col(t) = -2 * spins.col(t).cwiseProduct(
    //            spins.col(mod_t((int64_t)t+1, num_trotter_slices)) +
    //            spins.col(mod_t((int64_t)t-1, num_trotter_slices))
    //            );
    //}
 
    // diffE = s * (beta/num_trotter_slices) * this->dE + (1/2.) *
    // log(tanh(beta* gamma * (1.0-s) /num_trotter_slices)) * this->dEtrot
  }
 
  inline static std::size_t mod_t(const std::int64_t a,
                                  const std::size_t num_trotter_slices) {
    // a -> [-1:num_trotter_slices]
    // return a%num_trotter_slices (a>0), num_trotter_slices-1 (a==-1)
    return (a + num_trotter_slices) % num_trotter_slices;
  }
 
  TrotterMatrix trotter_spins;
 
  const SparseMatrixXx interaction;
 
  std::size_t num_classical_spins; // trotter_spins[0].size()-1
 
  FloatType gamma;
 
  TrotterMatrix rand_pool;
 
  TrotterMatrix dE;
};
 
template <typename FloatType> struct TransverseIsing<graph::CSRSparse<FloatType>> {
  using system_type = transverse_field_system;
 
  // matrix (row major)
  using SparseMatrixXx = Eigen::SparseMatrix<FloatType, Eigen::RowMajor>;
  // trotter matrix (col major)
  using TrotterMatrix =
      Eigen::Matrix<FloatType, Eigen::Dynamic, Eigen::Dynamic, Eigen::ColMajor>;
 
  TransverseIsing(const TrotterSpins &init_trotter_spins,
                  const graph::CSRSparse<FloatType> &init_interaction,
                  FloatType gamma)
      : trotter_spins(
            utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
                init_trotter_spins)),
        interaction(init_interaction.get_interactions()),
        num_classical_spins(init_trotter_spins[0].size()), gamma(gamma) {
    if (!(init_trotter_spins.size() >= 2)) {
      throw std::invalid_argument(
          "trotter slices must be equal or larger than 2.");
    }
 
    // initialize rand_pool
    rand_pool = TrotterMatrix(num_classical_spins + 1, trotter_spins.cols());
 
    // reset dE
    reset_dE();
  }
 
  TransverseIsing(const graph::Spins &init_classical_spins,
                  const graph::CSRSparse<FloatType> &init_interaction,
                  const FloatType gamma, const size_t num_trotter_slices)
      : interaction(init_interaction.get_interactions()),
        num_classical_spins(init_classical_spins.size()), gamma(gamma) {
    // initialize trotter_spins with classical_spins
 
    // assert(init_classical_spins.size() >= 2);
    if (!(num_trotter_slices >= 2)) {
      throw std::invalid_argument(
          "trotter slices must be equal or larger than 2.");
    }
 
    TrotterSpins init_trotter_spins(num_trotter_slices);
 
    for (auto &spins : init_trotter_spins) {
      spins = init_classical_spins;
    }
 
    // init trotter_spins
    trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // initialize rand_pool
    rand_pool = TrotterMatrix(num_classical_spins + 1, trotter_spins.cols());
 
    // reset dE
    reset_dE();
  }
 
  void reset_spins(const TrotterSpins &init_trotter_spins) {
    this->trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // reset dE
    reset_dE();
  }
 
  void reset_spins(const graph::Spins &classical_spins) {
    TrotterSpins init_trotter_spins(
        trotter_spins.cols()); // cols -> num_trotter_slices
 
    for (auto &spins : init_trotter_spins) {
      spins = classical_spins;
    }
    // init trotter_spins
    this->trotter_spins =
        utility::gen_matrix_from_trotter_spins<FloatType, Eigen::ColMajor>(
            init_trotter_spins);
 
    // reset dE
    reset_dE();
  }
 
  inline void reset_dE() {
    // reset dE and dEtrot
 
    // initialize dE (spatial direction)
    // we store only dE for spatial direction
    const auto &spins = this->trotter_spins;
    // std::size_t num_trotter_slices = this->trotter_spins.cols();
 
    this->dE = -2 * spins.cwiseProduct(this->interaction * spins);
 
    // for trotter direction
    // this->dEtrot = TrotterMatrix::Zero(num_classical_spins+1,
    // num_trotter_slices); for(std::size_t t=0; t<num_trotter_slices; t++){
    //    this->dEtrot.col(t) = -2 * spins.col(t).cwiseProduct(
    //            spins.col(mod_t((int64_t)t+1, num_trotter_slices)) +
    //            spins.col(mod_t((int64_t)t-1, num_trotter_slices))
    //            );
    //}
 
    // diffE = s * (beta/num_trotter_slices) * this->dE + (1/2.) *
    // log(tanh(beta* gamma * (1.0-s) /num_trotter_slices)) * this->dEtrot
  }
 
  inline static std::size_t mod_t(const std::int64_t a,
                                  const std::size_t num_trotter_slices) {
    // a -> [-1:num_trotter_slices]
    // return a%num_trotter_slices (a>0), num_trotter_slices-1 (a==-1)
    return (a + num_trotter_slices) % num_trotter_slices;
  }
 
  TrotterMatrix trotter_spins;
 
  const SparseMatrixXx interaction;
 
  std::size_t num_classical_spins; // trotter_spins[0].size()-1
 
  FloatType gamma;
 
  TrotterMatrix rand_pool;
 
  TrotterMatrix dE;
};
 
template <typename GraphType>
auto make_transverse_ising(const TrotterSpins &init_trotter_spins,
                           const GraphType &init_interaction,
                           const typename GraphType::value_type gamma) {
  return TransverseIsing<GraphType>(init_trotter_spins, init_interaction,
                                    gamma);
}
 
template <typename GraphType>
auto make_transverse_ising(const graph::Spins &classical_spins,
                           const GraphType &init_interaction,
                           const typename GraphType::value_type gamma,
                           const std::size_t num_trotter_slices) {
  return TransverseIsing<GraphType>(classical_spins, init_interaction, gamma,
                                    num_trotter_slices);
}
} // namespace system
} // namespace openjij