Dear Matthias, Thanks for your reply. At this point I do not really require these extreme situations. My question comes mainly from curiosity. I agree that parameters are a little extreme and far from the values one typically considers for "professional applications". It just results from playing around with the program - I would like to understand most features and limitations of the program.
Regards, Mateusz
Indeed your reasoning is correct. With that value of K you get a huge potential in the corners. Do you really want K=0.01 with L=100? Also the temperature is extremely low for the simulation of trapped bosonic atoms in optical lattices. The simplest solution is just reducing L. As you said that helps, and if a few sites all around the boundary are empty then the system size is large enough. If that does not help then I can look for a quick fix.
Matthias
On 28 Dec 2011, at 21:05, Mateusz Łącki wrote:
Dear All I would like to thanks Matthias for all the answers.
I have been playing with worm binary today. I have a question regarding the error message I am getting.
I have added harmonic trap to the BH hamiltonian (via adding additional parameter K as presented in the alps documentation - the one published as an article - I added K*n(i)*(L/2-x)*(L/2-x)).
But when the temperature is getting lower and lower the following error appears:
Exceeding std::numeric_limits<double>::max() in integrated weight
These are the parameters:
LATTICE="inhomogeneous open chain lattice"; L=100;
MODEL="trapped boson Hubbard"; NONLOCAL=0; U = 1.0; mu = 2.5; Nmax = 5;
T=0.01; t=0.05; K=0.01
MEASURE_LOCAL[Occupation] = "n"; THERMALIZATION=10000; SWEEPS=100000;
{ mu=2.5 }
This is the case when a few atoms are present in the middle of the trap, but the lattice is empty. If one changes K to 0.001 then sites near the boundary are filled and there is no error. The same is when one changes L to 50 - only a few sites near the boundary are empty. It seems as if much too large local energy causes the error (and the larger L the larger local energy of sites near the boundary, as well as if the trap's curvature is big). I would like to ask for a comment on my calculations and assumptions regarding the root cause for the error. I would like to ask for a possible solution to the problem: how to get rid of this error altogether (maybe using higher precision of floats could be forced by recompilation?)
Regards, Mateusz Łącki