int main(void){ #ifdef CHEMPS2_MPI_COMPILATION CheMPS2::MPIchemps2::mpi_init(); #endif CheMPS2::Initialize::Init(); //Square 2D Hubbard model with PBC const int L_linear = 3; // Linear size const int L_square = L_linear * L_linear; // Number of orbitals const int group = 0; // C1 symmetry const double U = 5.0; // On-site repulsion const double T = -1.0; // Hopping term const int N = 9; // Number of electrons const int TwoS = 1; // Two times the spin const int Irrep = 0; // Irrep = A (C1 symmetry) //Create the Hamiltonian (eightfold permutation symmetry is OK for site basis) int * irreps = new int[L_square]; for (int cnt=0; cnt<L_square; cnt++){ irreps[cnt] = 0; } //The Hamiltonian initializes all its matrix elements to 0.0 CheMPS2::Hamiltonian * Ham = new CheMPS2::Hamiltonian(L_square, group, irreps); delete [] irreps; //Fill with the site-basis matrix elements for (int cnt=0; cnt<L_square; cnt++){ Ham->setVmat(cnt,cnt,cnt,cnt,U); } for (int ix=0; ix<L_linear; ix++){ for (int iy=0; iy<L_linear; iy++){ const int idx1 = ix + L_linear * iy; // This site const int idx2 = (( ix + 1 ) % L_linear) + L_linear * iy; // Right neighbour (PBC) const int idx3 = ix + L_linear * ((( iy + 1 ) % L_linear)); //Upper neighbour (PBC) Ham->setTmat(idx1,idx2,T); Ham->setTmat(idx1,idx3,T); } } //The problem object 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, 500, 1e-10, 3, 0.05); OptScheme->setInstruction(1, 1000, 1e-10, 10, 0.0 ); //Run ground state calculation CheMPS2::DMRG * theDMRG = new CheMPS2::DMRG(Prob, OptScheme); const double EnergySite = theDMRG->Solve(); theDMRG->calc2DMandCorrelations(); //Clean up DMRG if (CheMPS2::DMRG_storeMpsOnDisk){ theDMRG->deleteStoredMPS(); } if (CheMPS2::DMRG_storeRenormOptrOnDisk){ theDMRG->deleteStoredOperators(); } delete theDMRG; //Hack: overwrite the matrix elements in momentum space (4-fold symmetry!!!) directly in the Problem object theDMRG = new CheMPS2::DMRG(Prob, OptScheme); // Prob->construct_mxelem() is called now for (int orb1=0; orb1<L_square; orb1++){ const int k1x = orb1 % L_linear; const int k1y = orb1 / L_linear; const double Telem1 = 2*T*( cos((2*M_PI*k1x)/L_linear) + cos((2*M_PI*k1y)/L_linear) ); for (int orb2=0; orb2<L_square; orb2++){ const int k2x = orb2 % L_linear; const int k2y = orb2 / L_linear; const double Telem2 = 2*T*( cos((2*M_PI*k2x)/L_linear) + cos((2*M_PI*k2y)/L_linear) ); for (int orb3=0; orb3<L_square; orb3++){ const int k3x = orb3 % L_linear; const int k3y = orb3 / L_linear; for (int orb4=0; orb4<L_square; orb4++){ const int k4x = orb4 % L_linear; const int k4y = orb4 / L_linear; const bool kx_conservation = (((k1x+k2x) % L_linear) == ((k3x+k4x) % L_linear))?true:false; const bool ky_conservation = (((k1y+k2y) % L_linear) == ((k3y+k4y) % L_linear))?true:false; double temp = 0.0; if ( kx_conservation && ky_conservation ){ temp += U/L_square; } if (( orb1 == orb3 ) && ( orb2 == orb4 )){ temp += (Telem1+Telem2)/(N-1); } Prob->setMxElement(orb1,orb2,orb3,orb4,temp); } } } } theDMRG->PreSolve(); // New matrix elements require reconstruction of complementary renormalized operators const double EnergyMomentum = theDMRG->Solve(); theDMRG->calc2DMandCorrelations(); //Clean up if (CheMPS2::DMRG_storeMpsOnDisk){ theDMRG->deleteStoredMPS(); } if (CheMPS2::DMRG_storeRenormOptrOnDisk){ theDMRG->deleteStoredOperators(); } delete theDMRG; delete OptScheme; delete Prob; delete Ham; //Check succes const bool success = ( fabs( EnergySite - EnergyMomentum ) < 1e-8 ) ? true : false; #ifdef CHEMPS2_MPI_COMPILATION CheMPS2::MPIchemps2::mpi_finalize(); #endif cout << "================> Did test 10 succeed : "; if (success){ cout << "yes" << endl; return 0; //Success } cout << "no" << endl; return 7; //Fail }
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 }