for O(2)U(1) symmetry 
Spins with two components: S=(S^{x},S^{y}) local field : h_{local}=(h_{local}^{x},h_{local}^{y}) Energy=S.h_{local}=h_{local}.cos(x) P(x)=e^{Energy/T}=e^{h.cos(x)} 
The Fast Linear Algorithm (FLA) uses the rejection method with a function consisting of n steps (see the figure and article for more details) 
1.  To use the Fast Linear Algorithm you must have :  


2.  AND you must have the tables in the file "O2.res". Two choices: . You can choose to download the file O2.res already done or make one with create_O2.out (.exe for windows), run it, and follow the instructions.  


