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/*
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 <string.h>
#include "Initialize.h"
#include "DMRG.h"
#include "FCI.h"
#include "MPIchemps2.h"
using namespace std;
void counter2bits( const int L, const int counter, int * bits, CheMPS2::Hamiltonian * ham, int * nelec, int * irrep ){
nelec[ 0 ] = 0;
irrep[ 0 ] = 0;
for ( int orb = 0; orb < L; orb++ ){
bits[ orb ] = ( counter & ( 1 << orb ) ) >> orb;
if ( bits[ orb ] == 1 ){
nelec[ 0 ] += bits[ orb ];
irrep[ 0 ] = CheMPS2::Irreps::directProd( irrep[ 0 ], ham->getOrbitalIrrep( orb ) );
}
}
}
int relative_phase( const int L, int * string_up, int * string_down ){
int phase = 1;
for ( int orb_down = 0; orb_down < L - 1; orb_down++ ){
if ( string_down[ orb_down ] == 1 ){
for ( int orb_up = orb_down + 1; orb_up < L; orb_up++ ){
if ( string_up[ orb_up ] == 1 ){
phase *= -1;
}
}
}
}
return phase;
}
int main(void){
#ifdef CHEMPS2_MPI_COMPILATION
CheMPS2::MPIchemps2::mpi_init();
#endif
CheMPS2::Initialize::Init();
// The Hamiltonian
const int psi4groupnumber = 7; // d2h -- see Irreps.h and N2.sto3g.out
const string matrixelements = "${CMAKE_SOURCE_DIR}/tests/matrixelements/N2.STO3G.FCIDUMP";
CheMPS2::Hamiltonian * Ham = new CheMPS2::Hamiltonian( matrixelements, psi4groupnumber );
cout << "The group was found to be " << CheMPS2::Irreps::getGroupName( Ham->getNGroup() ) << endl;
// Look at six symmetry sectors
const int Nelec = 14;
const int num_sectors = 6;
int TwoS[] = { 0, 2, 4, 4, 2, 2 };
int Irreps[] = { 0, 5, 0, 5, 2, 6 };
double E_dmrg[ 6 ]; // DMRG energy
double E_fci [ 6 ]; // FCI energy
double C_dev [ 6 ]; // RMS difference of DMRG and FCI coefficients
double S_fci [ 6 ]; // FCI spin squared
for ( int sector = 0; sector < num_sectors; sector++ ){
// The targeted symmetry sector and the Hamiltonian form together a FCI problem
CheMPS2::Problem * prob = new CheMPS2::Problem( Ham, TwoS[ sector ], Nelec, Irreps[ sector ] );
// To perform DMRG, a set of convergence instructions should be provided
CheMPS2::ConvergenceScheme opt_scheme( 2 );
// ConvergenceScheme::set_instruction( counter, virtual_dimension, energy_convergence, max_sweeps, noise_prefactor, dvdson_rtol );
opt_scheme.set_instruction( 0, 500, 1e-10, 2, 0.0, 1e-5 );
opt_scheme.set_instruction( 1, 1000, 1e-10, 30, 0.0, 1e-10 ); // Tight convergence for accurate FCI coefficients
// Do DMRG calculation
CheMPS2::DMRG * dmrg_solver = new CheMPS2::DMRG( prob, &opt_scheme );
E_dmrg[ sector ] = dmrg_solver->Solve();
dmrg_solver->calc2DMandCorrelations();
//Perform full configuration interation
#ifdef CHEMPS2_MPI_COMPILATION
if ( CheMPS2::MPIchemps2::mpi_rank() == MPI_CHEMPS2_MASTER )
#endif
{
const int nelec_up = ( Nelec + TwoS[ sector ] ) / 2;
const int nelec_down = ( Nelec - TwoS[ sector ] ) / 2;
const double workmem_mb = 10.0;
const int verbose = 1;
CheMPS2::FCI * fci_solver = new CheMPS2::FCI( Ham, nelec_up, nelec_down, Irreps[ sector ], workmem_mb, verbose );
double * GSvector = new double[ fci_solver->getVecLength( 0 ) ];
fci_solver->ClearVector( fci_solver->getVecLength( 0 ), GSvector );
GSvector[ fci_solver->LowestEnergyDeterminant() ] = 1.0;
E_fci[ sector ] = fci_solver->GSDavidson( GSvector );
S_fci[ sector ] = fci_solver->CalcSpinSquared( GSvector );
{ //Compare the FCI and DMRG determinant coefficients
int maxcount = 1;
for ( int orb = 0; orb < Ham->getL(); orb++ ){ maxcount *= 2; }
int n_up;
int n_down;
int irrep_up;
int irrep_down;
int * string_up = new int[ Ham->getL() ];
int * string_down = new int[ Ham->getL() ];
double rms_error1 = 0.0;
double rms_error2 = 0.0;
for ( int count_up = 0; count_up < maxcount; count_up++ ){
counter2bits( Ham->getL(), count_up, string_up, Ham, &n_up, &irrep_up );
if ( n_up == nelec_up ){
for ( int count_down = 0; count_down < maxcount; count_down++ ){
counter2bits( Ham->getL(), count_down, string_down, Ham, &n_down, &irrep_down );
if (( n_down == nelec_down ) && ( CheMPS2::Irreps::directProd( irrep_up, irrep_down ) == Irreps[ sector ] )){
const double coeff_dmrg = dmrg_solver->getFCIcoefficient( string_up, string_down, false );
const double coeff_fci = fci_solver->getFCIcoeff( string_up, string_down, GSvector );
const double phase_diff = relative_phase( Ham->getL(), string_up, string_down );
const double temp1 = coeff_dmrg - phase_diff * coeff_fci;
const double temp2 = coeff_dmrg + phase_diff * coeff_fci;
rms_error1 += temp1 * temp1;
rms_error2 += temp2 * temp2;
}
}
}
}
C_dev[ sector ] = sqrt( ( rms_error1 < rms_error2 ) ? rms_error1 : rms_error2 ); // The global phase of the wavefunction is arbitrary, hence.
cout << "RMS difference FCI and DMRG determinant coefficients = " << C_dev[ sector ] << endl;
delete [] string_up;
delete [] string_down;
}
delete [] GSvector;
delete fci_solver;
}
//Clean up
if ( CheMPS2::DMRG_storeMpsOnDisk ){ dmrg_solver->deleteStoredMPS(); }
if ( CheMPS2::DMRG_storeRenormOptrOnDisk ){ dmrg_solver->deleteStoredOperators(); }
delete dmrg_solver;
delete prob;
}
#ifdef CHEMPS2_MPI_COMPILATION
CheMPS2::MPIchemps2::broadcast_array_double( E_fci, num_sectors, MPI_CHEMPS2_MASTER );
CheMPS2::MPIchemps2::broadcast_array_double( C_dev, num_sectors, MPI_CHEMPS2_MASTER );
#endif
// Clean up the Hamiltonian
delete Ham;
// Check success
bool success = true;
for ( int sector = 0; sector < num_sectors; sector++ ){
success = ( success ) && ( fabs( E_dmrg[ sector ] - E_fci[ sector ] ) < 1e-8 );
success = ( success ) && ( C_dev[ sector ] < 1e-5 );
success = ( success ) && ( fabs( S_fci[ sector ] - 0.25 * TwoS[ sector ] * ( TwoS[ sector ] + 2 ) ) < 1e-8 );
}
#ifdef CHEMPS2_MPI_COMPILATION
CheMPS2::MPIchemps2::mpi_finalize();
#endif
cout << "================> Did test 1 succeed : ";
if ( success ){
cout << "yes" << endl;
return 0; //Success
}
cout << "no" << endl;
return 7; //Fail
}
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