Function fann_set_rprop_decrease_factor 

pub unsafe extern "C" fn fann_set_rprop_decrease_factor(
    ann: *mut fann,
    rprop_decrease_factor: c_float,
)

The decrease factor is a value smaller than 1, which is used to decrease the step size during RPROP training.

See also

fann_get_rprop_decrease_factor

This function appears in FANN >= 1.2.0.