Jörg Knappen wrote on Mon, Feb 4, 2013 08:35 AM UTC:
Jeremy, I don't do a mobility calculation. I just steal Ralph Betza's idea for mobility calculation to do an interpolation of piece values. Both endpoints (the values of wazir and rook, e.g.) are empirical piece values coming from playtesting; therefore the interpolated values are also piece values including all the factors affecting the piece value.
And yes, it is only an interpolation, not a calculation from first principles. I think there is still some point in it, seeing the different values of "magic" for Rook, Bishop, and Queen. And seeing that an "unchained" bishop is worth almost a rook maybe explains the surprising fact that the Janus/Paladin/Archbishop is worth almost a Chancellor/Marshall. At least, this is my current interpretation of the data.
The next riddle to solve is What constitutes the pair bonus?