DMRG.hpp

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#ifndef _H_DMRG_
#define _H_DMRG_
 
#include "cytnx_error.hpp"
#include "Device.hpp"
#include "intrusive_ptr_base.hpp"
#include "UniTensor.hpp"
#include <iostream>
#include <fstream>
#include "utils/vec_clone.hpp"
#include "Accessor.hpp"
#include <vector>
#include <initializer_list>
#include <string>
#include "tn_algo/MPS.hpp"
#include "tn_algo/MPO.hpp"
 
#ifdef BACKEND_TORCH
#else
  #include "backend/Scalar.hpp"
 
namespace cytnx {
  namespace tn_algo {
    class DMRG_impl : public intrusive_ptr_base<DMRG_impl> {
     private:
     public:
      MPS mps;
      MPO mpo;
 
      // for getting excited states:
      std::vector<MPS> ortho_mps;
      double weight;
 
      // iterative solver param:
      cytnx_int64 maxit;
      cytnx_int64 krydim;
 
      // environ:
      std::vector<UniTensor> LR;
      std::vector<std::vector<UniTensor>> hLRs;  // excited states
 
      friend class MPS;
      friend class MPO;
 
      void initialize();
      Scalar sweep(const bool &verbose, const cytnx_int64 &maxit, const cytnx_int64 &krydim);
      Scalar sweepv2(const bool &verbose, const cytnx_int64 &maxit, const cytnx_int64 &krydim);
    };
 
    // API
    class DMRG {
     private:
     public:
      boost::intrusive_ptr<DMRG_impl> _impl;
      DMRG(MPO mpo, MPS mps, std::vector<MPS> ortho_mps = {}, const double &weight = 30)
          : _impl(new DMRG_impl()) {
        // currently default init is DMRG_impl;
 
        // mpo and mps:
        this->_impl->mpo = mpo;
        this->_impl->mps = mps;
 
        // for getting excited states:
        this->_impl->ortho_mps = ortho_mps;
        this->_impl->weight = weight;
      };
 
      DMRG(const DMRG &rhs) { _impl = rhs._impl; }
 
      DMRG &operator=(const DMRG &rhs) {
        _impl = rhs._impl;
        return *this;
      }
 
      DMRG &initialize() {
        this->_impl->initialize();
        return *this;
      }
 
      // return the current energy
      Scalar sweep(const bool &verbose = false, const cytnx_int64 &maxit = 4000,
                   const cytnx_int64 &krydim = 4) {
        return this->_impl->sweep(verbose, maxit, krydim);
      }
 
      // return the current energy
      Scalar sweepv2(const bool &verbose = false, const cytnx_int64 &maxit = 4000,
                     const cytnx_int64 &krydim = 4) {
        return this->_impl->sweepv2(verbose, maxit, krydim);
      }
    };
 
  }  // namespace tn_algo
}  // namespace cytnx
 
#endif  // BACKEND_TORCH
 
#endif