getError() returns the error before the last iteration

[gnitr]

TrainFlatNetworkResilient.getError() returns the error measured before the last call to TrainFlatNetworkResilient.train().

It would be nice to document that behaviour in the function as it can be surprising.

You can observe the issue by replacing the end of XORFlat.ava with this block. You'll see that the mse is different from the one displayed with getError after the the last iteration.

    double[] output = new double[1];
    // test the neural network
    System.out.println("Neural Network Results:");
    double mse = 0;
    for(MLDataPair pair: trainingSet ) {
        double[] input = pair.getInput().getData();
        network.compute(input, output);
        System.out.println(input[0] + "," + input[1] + ":" + output[0]);
        mse += (output[0] - pair.getIdeal().getData()[0]) * (output[0] - pair.getIdeal().getData()[0]); 
    }
    System.out.println("MSE: "+(mse / trainingSet.getRecordCount()));
    train.iteration();
    System.out.println("Error: "+train.getError());

Since your stopping condition in XORFlat.java is based on getError() it actually runs one unnecessary iteration. So this type of construct is a bit misleading because in some cases the MSE can increase from one epoch to the next and the actual MSE of the network when you leave the loop might not meet the stopping condition. However in general I don't think it will make a huge difference though.

[seemasingh]

Good point! I added a better comment to Encog 3.1. This has been checked in.