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:
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.
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.
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
Dear Oleh,
On 2014/10/04, at 2:58, Menchyshyn Oleh oleh.menchyshyn@gmail.com wrote:
- 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.
The latter. The simple cubic lattice has tree intercell bonds (or edges) per unit cell.
- 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?
Yes. Just start your simulation again. The ALPS scheduler will find the latest checkpoints and continues the calculation from the point where the last checkpoints were taken.
Best, Synge
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