The tempfile is written very often during a simulation, depending on the optimization algorithm. It should contain the potential with the currently lowest sum of squares.

This file can be used to plot the current potential to see if it maybe contains some unwanted features.

Every time a new minimum in the sum of squares is discovered, the tempfile is written.

Same as Simulated Annealing, tempfile should always contain the potential with the lowest sum of squares.

Once every time the outer loop has successfully completed. This means after every line that is written to standard output the tempfile is written.