Restart DMRG with stored MPS

ITensor Julia Questions
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1

Dear professors,

Recently, I use Julia Itensor to calculate the two-dimensional Hubbard model.

I define my sites and MPO.

sites = siteinds("Electron", N ; conserve_qns=true, conserve_sz=false);

H = MPO(os, sites);

psi_init = random_mps(sites, state);

energy1, psi1 = dmrg(H, psi_init; nsweeps, maxdim, cutoff, noise, observer = obs, outputlevel = 1);

For the convenience of increasing maxdim in subsequent calculations, I have stored psi1.

f = h5open("FE_$indexx _state_1.h5","w");
write(f,"psi1",psi1);
close(f);

Now I intend to restart the program and increase the maxdim

sites = siteinds("Electron", N ; conserve_qns=true, conserve_sz=false);

H = MPO(os, sites);

f = h5open("FE_12 _state_1.h5","r")
psi_init = read(f,"psi1",MPS)
close(f);

energy1, psi1 = dmrg(H, psi_init; nsweeps, maxdim, cutoff, noise, observer = obs, outputlevel = 1);

An error occurs, MPO A and MPS B must share site indices.

I realize that my stored MPS has different site indexs and link indexs from the current MPO. Is there any good way to solve this problem?

Regards,
YD Shen.

2

Hello professors, I think I have solved this problem.

f = h5open("FE_12 _state_1.h5","r")
psi_shen = read(f,"psi1",MPS)
close(f);
psi_init = replace_siteinds(psi_shen, sites);

Thank you very much for your efforts!!

3

Two quick comments:
I would recommend the do syntax for opening the h5 object:

psi_shen = h5open("FE_12 _state_1.h5","r") do f
    read(f,"psi1",MPS)
end

And while your solution definitely works, may I recommend instead using the sites from the read in MPS:

sites = siteinds(psi_shen)

and pass this to the MPO etc to keep consistent site indices throughout all your calculations