test4.cpp.in

/*
   CheMPS2: a spin-adapted implementation of DMRG for ab initio quantum chemistry
   Copyright (C) 2013-2018 Sebastian Wouters

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License along
   with this program; if not, write to the Free Software Foundation, Inc.,
   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include <iostream>
#include <math.h>

#include "Initialize.h"
#include "DMRG.h"
#include "FCI.h"
#include "MPIchemps2.h"

using namespace std;

int main(void){

   #ifdef CHEMPS2_MPI_COMPILATION
   CheMPS2::MPIchemps2::mpi_init();
   #endif

   CheMPS2::Initialize::Init();
   
   //The Hamiltonian: 1D Hubbard model
   const int L = 10;
   const int Group = 0;
   const double U = 2.0;
   const double T = -1.0;
   int * irreps = new int[L];
   for (int cnt=0; cnt<L; cnt++){ irreps[cnt] = 0; }
   //The Hamiltonian initializes all its matrix elements to 0.0
   CheMPS2::Hamiltonian * Ham = new CheMPS2::Hamiltonian(L, Group, irreps);
   delete [] irreps;
   for (int cnt=0; cnt<L; cnt++){ Ham->setVmat(cnt,cnt,cnt,cnt,U); }
   for (int cnt=0; cnt<L-1; cnt++){ Ham->setTmat(cnt,cnt+1,T); }
   
   //The targeted state
   const int TwoS = 5;
   const int N = 9;
   const int Irrep = 0;
   CheMPS2::Problem * Prob = new CheMPS2::Problem(Ham, TwoS, N, Irrep);
   
   //The convergence scheme
   CheMPS2::ConvergenceScheme * OptScheme = new CheMPS2::ConvergenceScheme(2);
   //OptScheme->setInstruction(instruction, DSU(2), Econvergence, maxSweeps, noisePrefactor);
   OptScheme->setInstruction(0,   30, 1e-10,  3, 0.1);
   OptScheme->setInstruction(1, 1000, 1e-10, 10, 0.0);
   
   //Run ground state calculation
   CheMPS2::DMRG * theDMRG = new CheMPS2::DMRG(Prob, OptScheme);
   const double EnergyDMRG = theDMRG->Solve();
   theDMRG->calc2DMandCorrelations();
   #ifdef CHEMPS2_MPI_COMPILATION
   if ( CheMPS2::MPIchemps2::mpi_rank() == MPI_CHEMPS2_MASTER )
   #endif
   {
      theDMRG->getCorrelations()->Print();
   }
   
   //Clean up DMRG
   if (CheMPS2::DMRG_storeMpsOnDisk){ theDMRG->deleteStoredMPS(); }
   if (CheMPS2::DMRG_storeRenormOptrOnDisk){ theDMRG->deleteStoredOperators(); }
   delete theDMRG;
   delete OptScheme;
   delete Prob;
   
   //Calculate FCI reference energy
   double EnergyFCI = 0.0;
   #ifdef CHEMPS2_MPI_COMPILATION
   if ( CheMPS2::MPIchemps2::mpi_rank() == MPI_CHEMPS2_MASTER )
   #endif
   {
      const int Nel_up   = ( N + TwoS ) / 2;
      const int Nel_down = ( N - TwoS ) / 2;
      const double maxMemWorkMB = 10.0;
      const int FCIverbose = 1;
      CheMPS2::FCI * theFCI = new CheMPS2::FCI(Ham, Nel_up, Nel_down, Irrep, maxMemWorkMB, FCIverbose);
      EnergyFCI = theFCI->GSDavidson(NULL);
      delete theFCI;
   }
   #ifdef CHEMPS2_MPI_COMPILATION
   CheMPS2::MPIchemps2::broadcast_array_double( &EnergyFCI, 1, MPI_CHEMPS2_MASTER );
   #endif
   
   //Clean up the Hamiltonian
   delete Ham;
   
   //Check succes
   const bool success = ( fabs( EnergyDMRG - EnergyFCI ) < 1e-8 ) ? true : false;
   
   #ifdef CHEMPS2_MPI_COMPILATION
   CheMPS2::MPIchemps2::mpi_finalize();
   #endif
   
   cout << "================> Did test 4 succeed : ";
   if (success){
      cout << "yes" << endl;
      return 0; //Success
   }
   cout << "no" << endl;
   return 7; //Fail

}