- One usually considers one of two methods to change .
- (a)
**Metropolis**--- generate uniformly about and accept or reject change based on- if
**r>1**(energy decreased), accept - if
**r<1**(energy increased), accept with probability**r**.

- if
- (b)
**Heat Bath**--- sometimes one can use ``exact'' method to generate a variable according to a given probability distribution. - That is, if distribution function
can be calculated and inverted.

- Here, we view
**H**as a function of with other spins fixed.

Geoffrey Fox, Northeast Parallel Architectures Center at Syracuse University, gcf@npac.syr.edu