In <cite>(Chen and Kuhn, 2011)</cite> , we manually set the 17 free parameters of AMBER (see section 3.2 of that paper). In the experiments reported below, we tuned the 18 free parameters -the original 17 plus the ordering metric v described in the previous section -automatically, using the downhill simplex method of (Nelder and Mead, 1965) as described in (Press et al., 2002) .