Dear All, I would like to answer to my own question. I have found that chkp_each works also for mps_optim (not only for mps_evolve) It enables to checkpoint every few iterations (for example every 100).
BTW setting chkp_each to 0 causes „division by zero“ error due to line 113 of a file: ./applications/dmrg/mps/mps_optim/dmrg_sim.hpp
113 if (stopped || (sweep+1) % chkp_each == 0 || (sweep+1) == parms["nsweeps“])
It also shows that turning off checkpointing altogether is not possible, but this is the line which has to be modified to switch it off.
Kind Regards, Mateusz Łącki