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Mating potential and piece values[Subject Thread] [Add Response]
H. G. Muller wrote on 2012-09-29 UTC
> How does the inclusion of Nightriders lead to a mutual perpetual check?

Sooner or later the engine encounters this motif in its search tree
(h=Nightrider):

h . . h
. . . .
. k . .
. . . .
. K . .
. R R .

Both kings can then move left-right, discovering checks on the opponent
with their Nightriders and Rooks. As checkks are extended in Fairy-Max
(i.e. it always searches all evasions when in check), it extends to infinit
depth.

Fairy-Max can be configured to do Crooked Bishops, but not Aanca. But I
could always change the code, of course. Yet is seems best to try WN first.
If both sides play with this piece in stead of R, it is not that important
how strong it is.

New results:

Commoners + Pawn vs B-pair (584 games) 58%

So the B-pair had an advantage of 7.5% against 2 Commoners, but when short
a Pawn they see that advantage reverse to -8%. That means they ae pretty
much halfway (and a Pawn is apparently worth 15.5%). This is actually the
same as Knights do against the B-pair. So the Commoners come out pretty
consistently now as exactly equal in value to Knight.

I also tried to test end-game value, by setting up positions like

1m4k1/ppp2ppp/8/8/8/8/PPP2PPP/1N4K1 w - -

with various permutations of k, m and n. This was won by the Commoner  in
932 games by 58.9%. (~56% of he games are draws there.) I have no idea yet
how much an extra Pawn would be worth in such a position, though. But even
a single Commoner seems to have a significant advantage over a Knight, in
such an end-game.