Yes, search instability due to knowledge holes is an important issue. Even if you have the correct knowledge for instance a "winning score" about the sacrifical pawn breakthrought pattern with an advanced trio on the fifth rank versus an opponent trio on the seventh rank, you need to evaluate all intermediate positions until a passer is established with winning score as well, even if up to two pawns down temporary. For instance if one evaluates (1) "correctly", but fails to evaluate (2) correctly both with white to move ...Karlo Bala wrote:Ending with passers and candidates are extremely unstable. What if white pawn is on c6 instead on c5? You never know if pawn will reach last row with check or not. Sometimes king is in pawn square but can not catch the pawn because of obstacles, etc. As far as I know Stockfish does not use unstoppable pawn evaluation anymore (for good reason).bhlangonijr wrote:Many evaluation terms which would essentially resemble the search part are already statically calculated in many engines, for instance unstoppable pawns, "mate at a glance", etc.Karlo Bala wrote: I don't think so. Human knows that he has a winning position because he can instantly calculate this line: 1. b6 cxb6 2. cxb6 axb6. 3. axb6 (a6). It is not enough just to look at position, especially if black king is on e6 rather then on f5. Point is that human knows when a position is not stable, so why not put programming effort in that direction. Static evaluation of your engine looks good enough.
I think you should be careful with a big penalties.
[d] 8/ppp5/8/PPP5/8/8/8/8 w - -
[d] 8/p7/pp6/2P5/8/8/8/8 w - -
Huge scores always have the risk that there are some exceptions and errors, f.i. with unstoppable pawns considering multiple threads alá Réti Study. But here, in Ben-Hur Carlos' position, the advanced open candidate even with up to two opponent guards but same number of helpers, may already be treated as passer, and since the opponent king is outside the candidates square b5-e5-e8, its evaluation score should be already "winning" or at least close to this position:
[d] 8/8/6pp/1P3k2/8/4PK2/8/8 w - -
Gerd