I have got some problem with the convergence recently. I was doing Iqdmrg calculations with Kondo model. My ground state energy kept decreasing linearly (-0.03) after 8 sweeps to 30 and more, and the observables calculated were not as I expected . I believed there were two reasons. Maybe my initial state was not mixed (good?) enough for it to keep from stucking at the "local minimum" excited state, or it was not converged yet. I have tried using different initial states and putting a noise term, it did improve a little bit, so my question was,
How do I determine if it is converged? Besides the energy, I think it would be helpful if I could calculate correlation function or electron density at every step to see if those quantities are converged. I know how to calculate them with a given psi, but how do I calculate them at every step? I found a argument called "Debuglevel" and "Quiet = false" for information between sweeps, will that be useful for determining the convergence?
Also, In traditional DMRG algorithm there is a truncation error determined by the sum of the abandoned eigenvalues of the density matrix at each step, and that is what we use to determine the convergence. Is there a similar quantity in Itensor to do the same job?
There is another small question about creating the sweeping table. If I wanted 70 sweeps with Maxm=100, and then 10 sweeps with Maxm=500, is there any way simpler other than copying Maxm=100 seventy times? I know if I wanted the remaining sweeps parameter to be the same I would just leave it unfilled.
Thank you very much.