The simplicity of the CG-MLE approach leaves little to accelerate once termination is cared for. In this section we explore two techniques which do not fit into previous sections. The first technique modifies the CG direction update formula, and is controlled by the dufunc parameter. This parameter is summarized in Table 5.24, and described in more detail below. The second technique replaces CG with a different nonlinear minimizer. As will be seen, the experiments below do not prompt any change to our CG-MLE implementation, and hence the LR description tree shown in Figure 5.15 is still valid.