Thank you for your answers, I think I understand much more now. I would like to clarify just 2 points: 1) I don't get why should I divide 48 by 3? What do you call a bond? - Is it a $ J_{i,j} ( S^x_i * S^x_j + S^y_i * S^y_j + S^z_i * S^z_j ) = J_{i,j} ((S_i, S_j)) $ ? Here I've denoted a scalar product with the double parentheses - Or is it just an edge in the lattice graph? - For example ...................... <EDGE><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="2" offset="0 0 0"/></EDGE> <EDGE><SOURCE vertex="1" offset="0 0 0"/><TARGET vertex="4" offset="-1 -1 0"/></EDGE> ...................... where the former is an intracell edge, and the later is an intercell edge. I meant I had the 48 such intra- and intercell edges together. 2) I know about --time-limit option, and the tutorial says: -- gives the time (in seconds) which the program should run before writing a final checkpoint and exiting Can I restart the simulation again and make the ALPS using the obtained output data to proceed further? I know it sounds stupid to interrupt the simulation to restart it later. Otherwise, I would need to talk to sysadmin to change privileges for my account, so my simulations could exceed 48 hours. Best regards, Oleh

Dear Oleh,

On 2014/10/01, at 21:40, Menchyshyn Oleh <oleh.menchyshyn@gmail.com> wrote:

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So in my case, having the lattice with 16 atoms unit cell and 48 intra and intercell bonds (coupling constants), means I would need to multiply the estimated expected time for some simple reference model by 48?

Since there are 3 bonds in a unit in my case, 48/3 = 16 would be the correct factor to be used.

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The THERMALIZATION and SWEEPS parameters are chosen to meet the relative errors set up for observables being measured. If we increase the size of the system, namely L=8,12,16,24,..., but leave the SWEEPS the same, the relative error increases and the accuracy of simulation drops, aren't they?

The increase of error bar will be very slow (or sometimes negligible) for the loop algorithm, as the autocorrelation time stays O(1) irrespective of the system size.

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I'm asking that to clarify the issue as the cluster I use limits the jobs running time to 48 hours.

And is it possible in principle in ALPS to stop the calculation and restart later as a new process? Or in that case when I need to analyse the QMC statistics manually?

You can use the command line option ??time-limit? to specify the time after which the program will write final checkpoints and terminate. The simulation will continue from the checkpoints when the program is executed again.

Please read http://alps.comp-phys.org/mediawiki/index.php/ALPS_using_the_command_line#Co... for more details.

Best, Synge