+1 vote
asked by (430 points)

Dear ITensor team,
Recently, I have construct Hubbard model in honeycomb lattice, but I execute the code, I find such error :
libc++abi.dylib: terminating with uncaught exception of type std::outofrange: vector
zsh: abort ./hubbard_2d

I guess this error is due to : auto H = toMPO(ampo);
when I convert other lattice (for example square lattice or triangular lattice), the code is works! I just imitate square.h formalism to construct honeycomb lattice. Is there any subtle in the constructing ? the following is my naive code :

include "itensor/all.h"

include "itensor/mps/lattice/honeycomb.h"

using namespace itensor;

int main(int argc, char *argv[])
int Nx = 4;
int Ny = 8;
double U = 8.0;
if(argc > 3)
U = std::stof(argv[3]);
if(argc > 2)
Ny = std::stoi(argv[2]);
if(argc > 1)
Nx = std::stoi(argv[1]);

auto N = Nx * Ny;
auto sites = Electron(N);

auto t = 1.0;

auto ampo = AutoMPO(sites);
auto lattice = honeycombLattice(Nx, Ny, {"YPeriodic = ", true});
for(auto j : lattice)
ampo += -t, "Cdagup", j.s1, "Cup", j.s2;
ampo += -t, "Cdagup", j.s2, "Cup", j.s1;
ampo += -t, "Cdagdn", j.s1, "Cdn", j.s2;
ampo += -t, "Cdagdn", j.s2, "Cdn", j.s1;
for(auto j : range1(N))
ampo += U, "Nupdn", j;

auto H = toMPO(ampo);

auto state = InitState(sites);
for(auto j : range1(N))
state.set(j, (j % 2 == 1 ? "Up" : "Dn"));

auto sweeps = Sweeps(15);
sweeps.maxdim() = 20, 60, 100, 100, 200, 400, 800, 2000, 3000;
sweeps.noise() = 1E-7, 1E-8, 1E-10, 0;
sweeps.cutoff() = 1E-6;


auto psi0 = randomMPS(state);
auto [energy,psi] = dmrg(H,psi0,sweeps,{"Quiet=",true});


return 0;

and this is my naive constructing honeycomb lattice code:



include "itensor/mps/lattice/latticebond.h"

namespace itensor {

LatticeGraph inline
honeycombLattice(int Nx,
int Ny,
Args const& args = Args::global())
auto yperiodic = args.getBool("YPeriodic",true);
// Periodicity on y is meaningless for one dimensional chain or a ladder
yperiodic = yperiodic && (Ny > 2);
auto N = NxNy;
//auto N = 2
NxNy; // transfer to x direction 2Nx; y direction Ny
auto Nbond = 3*N-Ny + (yperiodic ? 0 : -Nx);
LatticeGraph latt;

for(int I = 1; I <= N; ++I)
    int xu = (I-1)/Ny+1; 
    int yu = (I-1)%Ny+1;
    int ni = 2*(I-1);

    latt.emplace_back(ni+2,ni+1,2*xu-1,yu,2*xu,yu); // inter-unitcell
    //X-direction bond
    if(xu < Nx) latt.emplace_back(ni+1,ni+2+2*Ny,2*xu,yu,2*(xu+1)-1,yu);

    if(Ny > 1)
        //diagonal bond
        if(yu < Ny) latt.emplace_back(ni+2,ni+1*2+1,2*xu-1,yu,2*xu,yu+1);
        //Periodic bond
        if(yperiodic && yu == 1) latt.emplace_back(ni+1,ni+2*(Ny-1)+2,2*xu,yu,2*xu-1,yu+Ny);
if(int(latt.size()) != Nbond) Error("Honeycomb latt wrong number of bonds");
return latt;

} //namespace itensor


Many thanks!

commented by (70.1k points)
Hi, did you check whether all of the j.s1 and j.s2 values are between [1,N] in your code that builds the AutoMPO?

commented by (430 points)
Hi Miles,
Thanks for your reply. Yes, i have check it.
commented by (70.1k points)
Thanks. How far does the code get before the crash happens? Is it after DMRG starts or before? Did you compile and run the code in debug mode to see if you get a better error message?

Thanks -
commented by (430 points)
Hi Miles,
The error  is happens before DMRG starts, I don't compile.the code in debug mode
commented by (70.1k points)
Which line of your code does the error happen on? Could you please add some printing statements and/or run your code in a debugger to determine this?
commented by (430 points)
Thanks Miles, I have solved my problem !
commented by (70.1k points)
Glad to hear it! Thanks for looking into it more

1 Answer

0 votes
answered by (70.1k points)

(Please see discussion above.)

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