Parameters for OnlineLogisticRegression function in Mahout

Can anyone tell me where do I find any documentation for parameters like:

-stepOffset

-alpha

-decayExponent

in an OnlineLogisticRegression function in Mahout?

I am interested in what do they change in calls like this one:

int FEATURES = 10000;       
OnlineLogisticRegression learningAlgorithm = new OnlineLogisticRegression(20, FEATURES, new L1())
                        .alpha(1).stepOffset(1000).decayExponent(0.9).lambda(3.0e-5).learningRate(20);