138 lines
3.1 KiB
C++
138 lines
3.1 KiB
C++
/** @file IsingModel.hpp
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*
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* @author Cory Alexander Balaton (coryab)
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* @author Janita Ovidie Sandtrøen Willumsen (janitaws)
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*
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* @version 0.1
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*
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* @brief The definition of the Ising model.
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*
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* @bug No known bugs
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* */
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#ifndef __ISING_MODEL__
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#define __ISING_MODEL__
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#include "constants.hpp"
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#include "data_type.hpp"
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#include "typedefs.hpp"
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#include "utils.hpp"
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#include <armadillo>
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#include <cstdint>
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#include <random>
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#include <unordered_map>
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#define INDEX(I, N) (I + N) % N
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// Indeces for the neighbor matrix.
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#define UP 0
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#define LEFT 0
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#define DOWN 1
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#define RIGHT 1
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/** @brief The Ising model in 2 dimensions.
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*
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* @details None of the methods are parallelized, as there is very little
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* benefit in doing so.
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* */
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class IsingModel {
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private:
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friend class IsingModelTest;
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/** @brief \f$ L \times L \f$ matrix where element \f$ x \in {-1, 1}\f$.
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* */
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arma::Mat<int> lattice;
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/** @brief \f$ L \times 2 \f$ matrix with the neighbors of each element
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* \f$ x_i \f$.
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*
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* @details The reason why it's \f$ L \times 2 \f$ instead of
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* \f$ L \times 2 \f$, is that we can see that we can use the same column
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* for the left and upper neighbor, and we can use the same column for the
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* right and lower neighbor.
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* */
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arma::Mat<int> neighbors;
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/** @brief A hash map containing all possible energy changes.
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* */
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//std::unordered_map<int, double> energy_diff;
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double energy_diff[17];
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/** @brief The temperature of the model.
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* */
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double T;
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/** @brief Size of the lattice.
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* */
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int L;
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/** @brief The current energy state. unit: \f$ J \f$.
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* */
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int64_t E;
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/** @brief The current magnetic strength. unit: Unitless.
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* */
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int64_t M;
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std::mt19937 engine;
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void initialize_engine();
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/** @brief Initialize the lattice with a random distribution of 1s and
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* -1s.
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* */
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void initialize_lattice();
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/** @brief initialize the neighbors matrix.
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* */
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void initialize_neighbors();
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/** @brief Initialize the hashmap with the correct values.
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* */
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void initialize_energy_diff();
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/** @brief Initialize the magnetization.
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* */
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void initialize_magnetization();
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/** @brief Initialize the energy.
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* */
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void initialize_energy();
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/** @brief Constructor used for testing.
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* */
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IsingModel();
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public:
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/** @brief Constructor for the Ising model.
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*
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* @param L The size of the lattice.
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* @param T The temperature for the system.
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* */
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IsingModel(int L, double T);
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/** @brief Constructor for the Ising model.
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*
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* @param L The size of the lattice.
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* @param T The temperature for the system.
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* @param val The value to set for all spins.
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* */
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IsingModel(int L, double T, int val);
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/** @brief The Metropolis algorithm.
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* */
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data_t Metropolis();
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/** @brief Get the current energy.
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*
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* @return double
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* */
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int get_E();
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/** @brief Get the current magnetization.
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*
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* @return double
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* */
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int get_M();
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};
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#endif
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