Author: Ulrich Tuerke
Date: 04:36:41 07/18/01
Go up one level in this thread
On July 18, 2001 at 06:00:32, Rafael Andrist wrote:
>My program missed to avoid a draw in a game (see below) due to some strange
>interactions between search and hash. I investigated it and recognized the
>following problem:
>
>- at move 33 my program recognizes a 2x and a 3x rep. during the search. The 2x
>rep. is allowed and the 3x is avoided. But in the hash, the move leading to a 3x
>rep. is stored.
>- I get PV completly from hash, so the displayed PV is incorrect (shows 3x rep.)
>but the real PV (inside the search) is correct
>- at move 35 my porgram gets the PV leading to a 3x rep. from hash. The PV has a
>length of 8 ply
>
>---> my program cannot search to 9 ply because it has not enough time (fixed
>time per move), so it takes the move recommended from hash and draws.
If I got you ríght, this should not happen.
Prior to probing the hash table, you should generally check whether the move
under consideration leads to an immediate draw. If so, the search can
immediately return from this candidate move with zero score.
The search over the remaining move then decides if it's favorable to select this
candidate.
Regards, Uli
>
>Has anyone a nice solution to this problem? Or is it so seldom that it can be
>ignored?
>
>Rafael B. Andrist
>
>
>[Event "Betatest"]
>[Site "Steffisburg"]
>[Date "2001.07.17"]
>[White "Wilhelm"]
>[Black "Der Bringer"]
>[Round "1"]
>[Result "1/2-1/2"]
>
>1. e2-e4 e7-e5 2. Ng1-f3 Nb8-c6 3. Bf1-b5 a7-a6 4. Bb5xc6 d7xc6 5. O-O f7-f6
>6. d2-d4 Bc8-g4 7. d4xe5 Qd8xd1 8. Rf1xd1 f6xe5 9. Rd1-d3 Bf8-d6 10. Nb1-d2
>Ng8-f6 11. Nd2-c4 O-O 12. Nf3xe5 Bg4-e2 13. Rd3-e3 Be2xc4 14. Ne5xc4 Nf6-g4 15.
>Re3-e2{7 0.35} Bd6xh2+ 16. Kg1-h1{7 0.31} Bh2-d6 17. f2-f3{8 0.31} Ng4-e5 18.
>Nc4xe5{7 0.35} Bd6xe5 19. c2-c3{7 0.36} Ra8-d8 20. Bc1-g5{7 0.36} Rd8-d3 21.
>Bg5-h4{7 0.36} Rf8-f7 22. Ra1-e1{7 0.44} Rf7-d7 23. Kh1-g1{7 0.42} g7-g6 24.
>Kg1-f2{7 0.48} Kg8-g7 25. Bh4-g3{8 0.45} Kg7-f6 26. f3-f4{8 0.43} Kf6-e6 27.
>Re2-e3{8 0.47} Rd3-d2+ 28. Re3-e2{8 0.47} Rd2-d3 29. Re2-e3{8 0.47} Rd3-d2+ 30.
>Re1-e2{9 0.48} Be5-g7 31. Re2xd2{8 0.46} Rd7xd2+ 32. Re3-e2{8 0.44} Rd2-d3 33.
>Re2-e3{8 0.44} Rd3-d2+ 34. Re3-e2{9 0.46} Rd2-d3 35. Re2-e3{8 0.44} Rd3-d2+
>1/2-1/2
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