H. G. Muller wrote on Sat, Dec 17, 2022 05:48 PM UTC:
Forcing the opponent's last remaining piece into a corner can never hurt. So it should probably be the dominant eval term. Fairy-Max doesn't have true PST; just a centralization bonus, and a weight for each piece type to multiply it. Originally that weight was 0 or 1, configurable by the user. When the King is bared, I now increase it to 10. I don't see any reason to discard other eval terms.
What holds to K-K distance in the bared case should probably hold for all short-range leapers. Removing their centralization drive does not help them seek out the bare King, even though it doesn't obstruct it. In Fairy-Max this was a problem in the KNFFK and KFFFK (Makruk!), where K + two pieces is enough to corner the King (and N + F even enough to trap it there), and then it had no incentive to approach the remaining piece(s), which are needed to execute the checkmate. You would probably see the same in KNNNK, certainly on large boards.
Of course forcing into a corner can backfire if it is the wrong corner (KBNK!). In Fairy-Max I solved this by switching to a centalization bonus that awards driving to another corner once the bare King visits one. The idea is that if there is a mate in the current corner, the search will always be deep enough to see it when the bare King is already trapped there.
With orthodox Kings (and a rectangular board) many pieces can be classified as minors with certainty: if they do not attack two orthogonally adjacent squares. That of course includes color-bounds. But also many more (all elementary obliques, Omega Wizard, Phoenix, Mamluk). Not all pieces that fail this test are majors, though. E.g. Silver or Wildebeest. But is seems a better criterion than piece value; the >500 criterion also gets the Wildebeest, Commoner, Gold and WD wrong. In I once made a Fairy-Max derivative 'Pair-o-Max' where I apply the color-binding and value criterion, but the user can force a piece to be considered a 'weak major'.
Other user-configured end-game properties in Pair-o-Max were 'defective pair' and 'strong defender', which could indicate KxxK or KQKx are draws, respectively.
Forcing the opponent's last remaining piece into a corner can never hurt. So it should probably be the dominant eval term. Fairy-Max doesn't have true PST; just a centralization bonus, and a weight for each piece type to multiply it. Originally that weight was 0 or 1, configurable by the user. When the King is bared, I now increase it to 10. I don't see any reason to discard other eval terms.
What holds to K-K distance in the bared case should probably hold for all short-range leapers. Removing their centralization drive does not help them seek out the bare King, even though it doesn't obstruct it. In Fairy-Max this was a problem in the KNFFK and KFFFK (Makruk!), where K + two pieces is enough to corner the King (and N + F even enough to trap it there), and then it had no incentive to approach the remaining piece(s), which are needed to execute the checkmate. You would probably see the same in KNNNK, certainly on large boards.
Of course forcing into a corner can backfire if it is the wrong corner (KBNK!). In Fairy-Max I solved this by switching to a centalization bonus that awards driving to another corner once the bare King visits one. The idea is that if there is a mate in the current corner, the search will always be deep enough to see it when the bare King is already trapped there.
With orthodox Kings (and a rectangular board) many pieces can be classified as minors with certainty: if they do not attack two orthogonally adjacent squares. That of course includes color-bounds. But also many more (all elementary obliques, Omega Wizard, Phoenix, Mamluk). Not all pieces that fail this test are majors, though. E.g. Silver or Wildebeest. But is seems a better criterion than piece value; the >500 criterion also gets the Wildebeest, Commoner, Gold and WD wrong. In I once made a Fairy-Max derivative 'Pair-o-Max' where I apply the color-binding and value criterion, but the user can force a piece to be considered a 'weak major'.
Other user-configured end-game properties in Pair-o-Max were 'defective pair' and 'strong defender', which could indicate KxxK or KQKx are draws, respectively.