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