55 lines
1.9 KiB
C++
55 lines
1.9 KiB
C++
#pragma once
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#include "model.hpp"
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#include "mps.hpp"
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#include <eigen3/Eigen/Eigen>
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#include <eigen3/unsupported/Eigen/CXX11/Tensor>
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#include <eigen3/unsupported/Eigen/MatrixFunctions>
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/**
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* @brief Apply the function f on every element if inRange, but reuse a cached result when two pointers point to the same object
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*/
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template<typename InType, typename OutType>
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std::vector<std::shared_ptr<OutType>> forEachUnique(std::function<OutType(const InType&)> f, const std::vector<std::shared_ptr<InType>>& inRange);
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template<typename T>
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using Bonds = std::vector<std::shared_ptr<e::Tensor<T, 4>>>;
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/**
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* @brief Apply time evolution on a bond
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* @details
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* \f[U = \exp{ B \, \del t} \f]
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*/
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template<typename T>
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e::Tensor<T, 4> getTimeEvolutionMatrix(const e::MatrixX<T>& bond, T dt, unsigned localDim);
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template<typename T>
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Bonds<T> getTimeEvolutionMatrices(const std::vector<std::shared_ptr<e::MatrixX<T>>>& bonds, T dt, unsigned int localDim);
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/**
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* @brief Apply U on bond i, perform SVD and truncate, update MPS
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*/
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template<typename T>
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void updateBond(MPS<T>& psi, size_t i, const e::Tensor<T, 4>& U, unsigned chiMax, T eps);
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template<typename T>
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using postUpdateFunction_t = std::function<void (const MPS<T>&, unsigned)>;
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template<typename T>
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void postUpdateNoop(const MPS<T>&, unsigned) {};
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/**
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* @brief Brickwall TEBS scheme
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* @details
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* Apply U on every second bond starting from the first,
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* then apply U on every second bond starting from the second
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*
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* First order scheme
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*
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* @param postUpdateFunc function that can be used to track expectation values after each update
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*/
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template<typename T>
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void runTEBD_brickwall(MPS<T>& psi, const Bonds<T>& bonds, unsigned chiMax, T eps, unsigned nSteps, postUpdateFunction_t<T> postUpdateFunc);
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template<typename T>
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void runTEBD_secondOrder(MPS<T>& psi, const Bonds<T>& bonds, const Bonds<T>& bondsHalfDT, unsigned chiMax, T eps, unsigned nSteps, postUpdateFunction_t<T> postUpdateFunc);
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