Zugzwang

[zullil]

It is not necessary. Now that Robolito SMP 1.0 was released, it can copy
directly. As he has done before

Can't we have one thread that focuses on chess and how engines attempt to play the game?

[lech]

Why can't Stockfish solve the second position:
[d] 4kr2/5p1K/3p1Q2/1p4P1/4P3/1PP5/7b/8 w - -
1.Kh6 Be5 2.Kg7 Bh2 3.c4 bxc4 4.e5 Bxe5 5.bxc4 +-

Maybe, I found the reason (bug in search ?).
Why "We want always alpha < beta " ?
Why in PV it is impossible: alpha = beta ?
It seems be important if e.g. value == VALUE_DRAW.
I changed it (added one sign to Stockfish 2.1.1) and now Stockfish found solution.

Code: Select all

 38/31	02:19	  36.527.523	262.141	 0,00	Qf6f5 Bh2e5 Qf5c8+ Ke8e7 Qc8b7+ Ke7e6 Qb7d5+ Ke6e7 Qd5b7+
 39/31	02:27	  38.510.445	261.087	 0,00	Qf6f5 Bh2e5 Qf5c8+ Ke8e7 Qc8b7+ Ke7e6 Qb7d5+ Ke6e7 Qd5b7+
 40/52	40:39	 548.604.547	224.941	+2,67	Kh7h6 Bh2e5 Kh6g7 Be5g3 c3c4 b5xc4 e4e5 Bg3xe5 b3xc4 Be5xf6+ g5xf6 Ke8d7 Kg7xf8 Kd7e6 Kf8g7 Ke6f5 Kg7xf7

[zullil]

Why can't Stockfish solve the second position:
[d] 4kr2/5p1K/3p1Q2/1p4P1/4P3/1PP5/7b/8 w - -
1.Kh6 Be5 2.Kg7 Bh2 3.c4 bxc4 4.e5 Bxe5 5.bxc4 +-

Maybe, I found the reason (bug in search ?).
Why "We want always alpha < beta " ?
Why in PV it is impossible: alpha = beta ?
It seems be important if e.g. value == VALUE_DRAW.
I changed it (added one sign to Stockfish 2.1.1) and now Stockfish found solution.

Code: Select all

 38/31	02:19	  36.527.523	262.141	 0,00	Qf6f5 Bh2e5 Qf5c8+ Ke8e7 Qc8b7+ Ke7e6 Qb7d5+ Ke6e7 Qd5b7+
 39/31	02:27	  38.510.445	261.087	 0,00	Qf6f5 Bh2e5 Qf5c8+ Ke8e7 Qc8b7+ Ke7e6 Qb7d5+ Ke6e7 Qd5b7+
 40/52	40:39	 548.604.547	224.941	+2,67	Kh7h6 Bh2e5 Kh6g7 Be5g3 c3c4 b5xc4 e4e5 Bg3xe5 b3xc4 Be5xf6+ g5xf6 Ke8d7 Kg7xf8 Kd7e6 Kf8g7 Ke6f5 Kg7xf7

You should highlight this by starting a new topic, especially if it involves a possible bug.