code: public void setBeta(double beta)
      {
          if(beta <= 0 || beta >= 1 || Double.isNaN(beta))
              throw new IllegalArgumentException("shrinkage term must be in (0, 1), not " +  beta);
          this.beta = beta;
      }
docs: Sets the shrinkage term used for the line search.
  @param beta the line search shrinkage term