void fann_set_quickprop_mu(struct fann * ann, float quickprop_mu);
The mu factor is used to increase and decrease the step-size during quickprop training. The mu factor should always be above 1, since it would otherwise decrease the step-size when it was suppose to increase it.
The default value for this parameter is 1.75.
This function appears in FANN >= 1.2.0.