The uniform sampling, also used for comparison in this work, allows drawing from constrained subsets with O(1) time. This implies that for near-uniform probability distributions the uniform sampling might outperform weighted sampling, after taking quality of excitation and iteration time into account. The possible sampling schemes are summarized in to be the fastest combination. In our earlier work using PCHB (AB|IJ)) to be the fastest combination. Note that directly sampling pairs IJ and AB can reduce the memory cost as described in reference 3, but is tied to a fast-weighted sampling scheme.