wolffd@0: function [reduced_pot,successful] = reduce(pot,tailnodes)
wolffd@0: % Executes the reduce operation defined in 
wolffd@0: % Stable Local Computation with Conditional Gaussian Distributions
wolffd@0: % Steffen L. Lauritzen
wolffd@0: % Frank Jensen
wolffd@0: % September 1999
wolffd@0: % The potential pot is reduced if B contains any zero columns 
wolffd@0: % The test are restricted to the positions in tailnodes.
wolffd@0: % Any columns successfully deleted are entered in the array successful
wolffd@0: 
wolffd@0: if nargin < 2
wolffd@0:     tailnodes = 1:pot.ctailsize;
wolffd@0: end
wolffd@0: 
wolffd@0: successful = [];
wolffd@0: 
wolffd@0: % Look for all columns beeing equal to zero
wolffd@0: for i = tailnodes
wolffd@0:     if ~any(pot.B(:,i))
wolffd@0:         successful = [successful i]; 
wolffd@0:     end
wolffd@0: end
wolffd@0: 
wolffd@0: remain = mysetdiff(1:pot.ctailsize,successful);
wolffd@0: 
wolffd@0: % Erase the zero-columns and decrease the tailsize
wolffd@0: pot.B = pot.B(:,remain);
wolffd@0: pot.ctailsize = pot.ctailsize - length(successful);
wolffd@0: 
wolffd@0: % Return the reduced potential
wolffd@0: reduced_pot = pot;
wolffd@0: