If you need to (want to) make your HUGIN network even faster than what you can achieve by ordinary compression, you can use the approximation option.

Approximation is activated in the Compilation tab of the Network Properties dialog box. This function works by eliminating the smallest table values of the internal network representation (making them zero), so that the compression function will be more efficient (compression can save space when there are a lot of zero probabilities).

To specify which table values to eliminate, you must set an epsilon value which specifies how much probability mass to eliminate. Then, small table values are set to zero - from the smallest end, until you have removed an amount of epsilon probability mass.

You should be careful when using approximation. It can cause conflicts when rare cases occur, since small (though existing) probability mass has been eliminated.