Or you can simply discard any non-conformed individuals, during any process (initialization, breeding). And keep generating new individuals until your population is filled with the individuals conforming to this rule. On Mon, Feb 24, 2014 at 1:13 PM, Sean Luke <[log in to unmask]> wrote: > Francisco, ECJ can't do this by default: and I really have no idea how to > require this constraint. You'll have to either enforce this rule in the > tree builder algorithm and/or the crossover mutation operators. > Alternatively you can assess the fitness of non-confirming individuals as > very low. > > Sean > > On Feb 24, 2014, at 6:57 AM, Francisco Lopez de la Franca < > [log in to unmask]> wrote: > > > Hello. > > > > I am new in ECJ. I'm going to use ECJ to find the solution of a second > degree equation, that is, x=(-b+sqrt(b^2-4ac))/(2a). > > I've implemented as FunctionSet the following nodes: add, sub, sqrt, > square, mul, div, neg, a, b, c, 2 and 4. > > I've followed the instructions described both in the tutorial4 in the > documentations provided with ECJ and the one in the ECJ manual. > > > > What I need and donot find the way, is to force to appear in the result > tree the nodes: a, b, c, 2, 4, -, +, sqrt, square, div and mul. That is, to > specify in some manner that the nodes must appear at least once. Moreover, > I'd like to know if it is possible to set that one node must appear a > number of times in the solution. > > > > I hope to have explained well. > > > > Thank you very much in advance. > > > > Regards. >