I'm trying to implement 10-fold cross validation in a GP classifier. I need to train and test 10 times with different partitions of the data. But when I try to run for the 2nd time Evolve.make, it returns a fatal error. It looks like since it's a static method, it is saving in its memory all the data read from the parameters file. Is there any option to restart the Evolutionary machine from zero? Am I doing something wrong? This is the sample code using the regression example. package ec.app.classification.family; import ec.*; public class Testing { public static void main(String[] args) { String paramFileName = "ec/app/regression/erc.params"; EvolutionState state = ec.Evolve.make(new String[] {"-file", paramFileName}); try { state.run(EvolutionState.C_STARTED_FRESH); } catch (Exception ex) { ex.printStackTrace(); System.exit(1); } EvolutionState state2 = ec.Evolve.make(new String[] {"-file", paramFileName}); try { state2.run(EvolutionState.C_STARTED_FRESH); } catch (Exception ex) { ex.printStackTrace(); System.exit(1); } } } And the output: ---------- java ---------- | ECJ | An evolutionary computation system (version 10) | Copyright 2003 by Sean Luke | URL: http://www.cs.umd.edu/projects/plus/ec/ecj/ | Mail: [log in to unmask] | Date: January 1, 2003 | Current Java: 1.4.2_03 / Java HotSpot(TM) Client VM-1.4.2_03-b02 | Suggested Minimum Java: 1.2.2 | Required Minimum Java: 1.1 Setting up Processing GP Types Processing GP Node Constraints Processing GP Function Sets Processing GP Tree Constraints {0.9994835008057914,3.9948376750832253}, ..... {0.4277701109521461,0.7225182028217614}, {0.3985343905631442,0.6458899940023977}, Initializing Generation 0 Generation 1 Generation 2 ... Generation 50 | ECJ | An evolutionary computation system (version 10) | Copyright 2003 by Sean Luke | URL: http://www.cs.umd.edu/projects/plus/ec/ecj/ | Mail: [log in to unmask] | Date: January 1, 2003 | Current Java: 1.4.2_03 / Java HotSpot(TM) Client VM-1.4.2_03-b02 | Suggested Minimum Java: 1.2.2 | Required Minimum Java: 1.1 Setting up Processing GP Types FATAL ERROR: The GP type "nil" has been defined multiple times. PARAMETER: gp.type.a.0.name Output completed (6 sec consumed) - Normal Termination Also tried with: EvolutionState state = ec.Evolve.make(new String[] {"-file", paramFileName, "-p","-nostore=true"}); Is that correct?