guyhaw
commented
8 years ago Got lucky - found Q7/6K1/P7/8/1b6/8/p7/3k4 b ... 1. ... a1=Q+ and 52 checks later, it's mate, 0-1. Black also has a frustrated win with the wK on h8 or d4, and (with the bP on b2 rather than a2) with the wK on h7 or g6. This accounts for all the five 0-1 frustrated wins in KQPKBP.
The statsfiles give examples of frustrated wins for White in '101', i.e., 1 ply. But they do not give examples frustrated wins for Black in '101', i.e. 1 ply.
There are four endgame where this and the omission occurs: KQNPKQ, KQRPKP, KRRPKP and KQPKBP. For the first three, I easily found exemplar frustrated wins: KQNPKQ/0-1: 4K1k1/1N1P4/8/3q4/8/1Q6/8/8 b, 1. ... Qxb3 {RdM's KNPKQ/0-1 example, pos 1w} KQRPKP/0-1: 8/1K6/8/2P5/2R5/7k/p7/1Q6 b, 1. ... axb1=Q+ {KRPKQ: dtz50' = 144p} KRRPKP/0-1: 8/1K6/8/2P5/2R5/7k/p7/1R6 b (similar), 1. ... axb1=Q+ {KRPKQ: dtz50' = 144p}
I have not found an exemplar longest frustrated win for KQPKBP/0-1 and this now seems to be the only lacuna in the list of exemplar frustrated wins - and so is on my 'much wanted' list.
A first inspection of the stats-p code shows no asymmetry re lcw_ply and glcw_ply v lcb_ply and glcb_ply. Is something asymmetric happening with the integer 'i'?
Sorry I cannot be more help - Guy