Correct way to store and extract mate scores

ianm · Post by **ianm** » Wed Jul 08, 2020 6:45 am

Hi All

I've confused myself with this (not surprising). So I'm wondering when extracting the mate score from the hash table does the score need to be adjusted by (+/- ply) or reset to the fixed mate value (+/- ply)?

Here's what I'm doing now:

Code: Select all

   if (ht[hi].key==hk && ht[hi].depth>=depth && (ht[hi].flag&FL_SIDE)==side)
   {
      int16_t s = ht[hi].score;
      if (s>MATE_VALUE) s -= ply; else if (s<-MATE_VALUE) s += ply;
      if (ht[hi].flag&HASH_EXACT) {stats.nhash++; return s;}
      else if ((ht[hi].flag&HASH_BETA) && s>=beta) {stats.nhash++; return beta;}
      else if ((ht[hi].flag&HASH_ALPHA) && s<=alpha) {stats.nhash++; return alpha;}
   }

but should it be:

Code: Select all

   if (ht[hi].key==hk && ht[hi].depth>=depth && (ht[hi].flag&FL_SIDE)==side)
   {
      int16_t s = ht[hi].score;
      if (s>MATE_VALUE) s = MAX_VALUE-ply; else if (s<-MATE_VALUE) s = -MAX_VALUE+ply;
      if (ht[hi].flag&HASH_EXACT) {stats.nhash++; return s;}
      else if ((ht[hi].flag&HASH_BETA) && s>=beta) {stats.nhash++; return beta;}
      else if ((ht[hi].flag&HASH_ALPHA) && s<=alpha) {stats.nhash++; return alpha;}
   }

In other words should the mate value from the hash table be adjusted to the current ply irrespective of the ply it was on when it was stored in the HT?

Many thanks, Ian

Sven · Post by **Sven** » Wed Jul 08, 2020 10:43 am

The typical pattern applied in many engines is as follows:

- In the tree, mate scores are relative to the root node. When detecting a mate ("mated in 0") you return -(MATE_VALUE - ply). When seeing a mate score returned from a subtree you either see a negative score ("mated in N" with even N) or a positive score ("mate in N" with odd N) but both contain the distance from the root node to the "mated in 0" node where the mate was originally detected.

- In the hash table, mate scores are relative to the position they belong to.

- Therefore you retrieve mate scores from TT by inserting the distance between root and current node (which makes positive mate scores smaller and negative ones greater):

Code: Select all

int16_t scoreFromTT(int16_t s, int16_t ply) { return (s > MATE_VALUE) ? s - ply : (s < -MATE_VALUE) ? s + ply : s; }
//...
int16_t treeScore = scoreFromTT(ht[hi].score, ply);

and you store mate scores in the TT by removing that distance (which makes positive mate scores greater and negative ones smaller):

Code: Select all

int16_t scoreToTT(int16_t s, int16_t ply) { return (s > MATE_VALUE) ? s + ply : (s < -MATE_VALUE) ? s - ply : s; }
// ...
ht[hi].score = scoreToTT(treeScore, ply);

So your current code is correct if you also do the reverse when storing ...

hgm · Post by **hgm** » Wed Jul 08, 2020 3:49 pm

For clarification: the same position in the TT can be probed at different distances from the root; even if there are no transpositions it will be probed such when it survives to the search for the next game move. So you cannot store any distance relative to the root in the TT, and must store absolute distance-to-mate there.

But if you retrieve a mate-in-7-ply from the TT at ply level 3 of your tree, you want it to show up as mated-in-10-ply in the root. If you don't adapt scores when propagating them to the root, you must make it such that the probe already delivers that score. (Except for the sign, which you do flip while propagating scores to the root.)

ianm · Post by **ianm** » Thu Jul 09, 2020 1:50 am

Excellent, thanks so much. I wasn't storing the value correctly. Interesting how it was working quite well though. Chess engines seem quite resilient until they play bad moves out of the blue!

Cheers, Ian

elcabesa · Post by **elcabesa** » Fri Jul 10, 2020 12:26 pm

When saving to TT you have to store: "from this node it's a mate in 3"

When reading from TT you have to translate it to: "from root node it's a mate in 5"

ianm · Post by **ianm** » Sat Jul 11, 2020 5:41 am

OK, I've modified the code to correctly store in the hash table and ran 100 games against TSCP. Plankton got a score of 83% which is the highest yet. But in game 6 where Plankton was clearly winning the game ended in a draw due to 3-fold repetition. Here is the game:

[pgn][Event "T15_Raz_Pru_Tap_Futility.at"]
[Site "RCH-DIV-GT250J2"]
[Date "2020.07.10"]
[Round "6"]
[White "TSCP181c"]
[Black "Plankton64_03"]
[Result "1/2-1/2"]
[BlackElo "2200"]
[ECO "D50"]
[Opening "QGD"]
[Time "12:57:22"]
[Variation "Semi-Tarrasch, Old Pillsbury Variation"]
[WhiteElo "2200"]
[TimeControl "0+3"]
[Termination "normal"]
[PlyCount "137"]
[WhiteType "human"]
[BlackType "human"]

1. c4 e6 2. Nc3 d5 3. d4 Nf6 4. Nf3 c5 5. Bg5 {(e2e3 b8d7 c4d5 f6d5 f1c4
d5c3 b2c3) +0.07/6 2} cxd4 {(c5xd4 Nf3xd4 d5xc4 Qd1-a4+ Nb8-d7 Qa4xc4 e6-e5
Nd4-c2 Bf8-e7 e2-e4 O-O O-O-O) +0.35/11 2} 6. Qxd4 {(d1d4 f8e7 c4d5 e6d5
e1c1 b8c6) +0.22/6 2} Nc6 {(Nb8-c6 Qd4-h4 Bf8-e7 O-O-O h7-h6 c4xd5 e6xd5
Bg5xf6 Be7xf6 Qh4-h5 d5-d4) +0.50/11 2} 7. Qh4 {(d4h4 d5c4 a1d1 d8b6 g5f6
b6b2 f6d4 c6d4 h4d4) +0.06/7 2} Be7 {(Bf8-e7 c4xd5 e6xd5 e2-e4 d5xe4 Nc3xe4
Nf6xe4 Qh4xe4 O-O Bg5xe7 Nc6xe7) +0.41/11 2} 8. O-O-O {(e1c1 e8g8 e2e4 h7h6
g5f6 e7f6) +0.25/6 2} h6 {(h7-h6 c4xd5 e6xd5 Bg5xf6 Be7xf6 Qh4-h5 Bf6xc3
b2xc3 Qd8-a5 Qh5xd5 Qa5xc3+) +0.37/11 2} 9. cxd5 {(c4d5 e6d5 e2e4 e8g8 g5f6
e7f6) +0.29/6 2} exd5 {(e6xd5 e2-e4 O-O Nc3xd5 Nf6xd5 Bg5xe7 Nc6xe7 e4xd5
Ne7xd5 Bf1-c4 Bc8-e6 Qh4xd8 Ra8xd8) +0.17/11 2} 10. Bxf6 {(g5f6 e7f6 h4f4
f6c3 f4e3 c8e6 e3c3) -0.04/6 2} Bxf6 {(Be7xf6 Qh4-a4 Qd8-b6 Qa4-a3 Bf6xc3
Qa3xc3 Qb6xf2 Qc3xg7 Qf2-c5+ Kc1-d2 Qc5-f8 Qg7-f6) +0.27/11 2} 11. Qa4
{(h4a4 f6c3 b2c3 e8g8 e2e4 c8e6 f1c4) -0.08/7 2} Bxc3 {(Bf6xc3 b2xc3 Qd8-f6
Rd1xd5 Qf6xc3+ Kc1-b1 O-O e2-e4 Bc8-e6 Rd5-d3 Qc3-c5 Nf3-d4 Nc6xd4 Rd3xd4)
+0.40/11 2} 12. bxc3 {(b2c3 d8f6 a4b3 e8g8 e2e3 c8g4 f1e2) -0.26/7 2} Qf6
{(Qd8-f6) +0.40/10 2} 13. Qa3 {(a4a3 c8e6 e2e3 e8c8 f1b5 h8e8 b5c6 b7c6)
-0.31/6 2} Be6 {(Bc8-e6 e2-e3 O-O-O Bf1-b5 Be6-g4 Bb5-e2 Kc8-b8 h2-h3
Bg4xf3 Be2xf3 Nc6-e5 Rd1xd5 Rd8xd5 Bf3xd5 Qf6xf2) +0.38/11 2} 14. e3 {(e2e3
e8c8 f1b5 d8e8 h2h4 h6h5 b5c6 b7c6) -0.30/6 2} O-O-O {(O-O-O Bf1-b5 Be6-g4)
+0.31/10 2} 15. h3 {(h2h3 d8e8 f1b5 h8h7 b5c6 b7c6) -0.30/6 2} Kb8 {(Kc8-b8
Bf1-b5 Rd8-c8 Bb5-d3 g7-g5 Kc1-b1 Be6-f5 Qa3-a4 Bf5-e6 Qa4-c2) +0.38/10 2}
16. Bb5 {(f1b5 c6e5 f3e5 f6e5 b5d3 d8c8) -0.15/6 2} Rc8 {(Rd8-c8 Bb5-d3)
+0.36/9 2} 17. Rd2 {(d1d2 f6e7 a3b2 h6h5 b5c6 c8c6) -0.16/6 2} Rc7 {(Rc8-c7
Kc1-b2 Nc6-e5 Nf3-d4 a7-a6 Bb5-f1 Be6-d7 g2-g4 Qf6-b6+ Qa3-b4 Qb6-f6)
+0.38/10 2} 18. Bxc6 {(b5c6 c7c6 f3d4 c6a6 a3c5 h8e8) -0.10/6 2} Rxc6
{(Rc7xc6 Nf3-d4 Rc6-a6 Qa3-b2 Ra6-b6 Qb2-a1 Qf6-g6 g2-g4) +0.20/10 2} 19.
Nd4 {(f3d4 c6a6 a3b4 h8e8 d2b2 f6e7) -0.10/6 2} Ra6 {(Rc6-a6 Qa3-b2 Ra6-b6
Qb2-a1 Be6-d7 g2-g3 Qf6-g6 Rd2-c2 Qg6-e4 Rh1-h2 f7-f5) +0.23/11 2} 20. Qb4
{(a3b4 f6g6 h1h2 h8e8 d2b2 a6b6) -0.10/6 2} Rb6 {(Ra6-b6 Qb4-a5 Qf6-g6
Nd4-b5 Rb6xb5 Qa5xb5 Qg6xg2 Qb5-f1 Qg2xf1+ Rh1xf1 Be6xh3 Rf1-g1) +1.04/11
2} 21. Qa5 {(b4a5 f6g6 d4b5 g6g2 a5a7 b8c8 a7b6 g2h1) -0.38/6 2} Qg6
{(Qf6-g6 Nd4-b5 Rb6xb5 Qa5xb5 Qg6xg2 Qb5-f1 Qg2xf1+ Rh1xf1 Be6xh3 Rf1-g1
Rh8-c8 Rg1xg7 Rc8xc3+) +0.72/11 2} 22. Nb5 {(d4b5 b6b5 a5b5 g6g2 h1d1 g2h3)
-0.49/6 2} Rxb5 {(Rb6xb5 Qa5xb5 Qg6xg2 Qb5-f1 Qg2xf1+ Rh1xf1 Be6xh3 Rf1-g1
g7-g5 Rd2xd5 Bh3-e6 Rd5-a5) +0.11/11 2} 23. Qxb5 {(a5b5 g6g2 b5f1 e6h3 f1d1
h8c8 d2d5 c8c3) -0.39/7 2} Qxg2 {(Qg6xg2 Qb5-f1 Qg2xf1+ Rh1xf1 Be6xh3
Rf1-g1 h6-h5 Rg1xg7 Bh3-e6 f2-f4 h5-h4 Kc1-c2) +0.12/11 2} 24. Qf1 {(b5f1
g2f1 h1f1 e6h3 f1g1 h8h7 d2d5 h6h5) +0.28/7 2} Qxf1+ {(Qg2xf1+ Rh1xf1
Be6xh3 Rf1-g1 g7-g6 Rd2xd5 Bh3-e6 Rd5-d2 h6-h5 e3-e4 Rh8-c8 Kc1-b2 h5-h4)
+0.51/12 2} 25. Rxf1 {(h1f1 e6h3 f1g1 h8h7 d2d5 h3e6 d5d8 b8c7 d8d2)
+0.14/7 2} Bxh3 {(Be6xh3 Rf1-g1 g7-g6 Rd2xd5 Bh3-e6 Rd5-d2 h6-h5 e3-e4)
+0.65/13 2} 26. Rg1 {(f1g1 g7g6 d2d5 h3e6 d5d2 h8c8 c1b2 h6h5) +0.09/8 3}
g6 {(g7-g6) +0.65/12 3} 27. Rxd5 {(d2d5 h3e6 d5d2 h8c8 c1b2 h6h5 e3e4)
+0.27/7 2} Be6 {(Bh3-e6 Rd5-d2 h6-h5 e3-e4 h5-h4 e4-e5 h4-h3 Rg1-h1 g6-g5
Rh1-h2 b7-b5 Kc1-b2) +0.57/12 3} 28. Rd2 {(d5d2 h6h5 e3e4 h5h4 f2f4 h4h3
c1d1 h3h2) -0.02/8 3} h5 {(h6-h5 e3-e4 h5-h4 e4-e5 h4-h3 Rg1-h1 g6-g5
Rh1-h2 Kb8-c7 a2-a4 b7-b6 Kc1-c2) +0.57/12 2} 29. e4 {(e3e4 h5h4 f2f4 h4h3
g1h1 b8c7 c1d1) -0.01/7 3} h4 {(h5-h4 e4-e5 Kb8-c7 f2-f4 h4-h3 Rd2-h2 b7-b5
Kc1-b2 a7-a5 Rg1-h1 Kc7-c6 Kb2-c2) +0.56/12 2} 30. f4 {(f2f4 h4h3 c1d1 h8h4
g1f1 h3h2 d2d8) -0.12/7 3} h3 {(h4-h3 e4-e5 Rh8-h4 Rg1-f1 Kb8-c7 Kc1-b2
b7-b5 Rf1-f2 Kc7-c6 a2-a3 Be6-d5 f4-f5) +0.57/12 2} 31. Rf1 {(g1f1 b8c7
c1d1 c7c6 f1h1 h8h4 h1f1) -0.21/7 3} Kc7 {(Kb8-c7 e4-e5 b7-b5 Kc1-b2 Kc7-c6
Rf1-f2 Be6-d5 Rf2-h2) +0.58/11 2} 32. a3 {(a2a3 f7f6 c1c2 c7c6 f1h1 h8h4
h1g1) -0.21/7 2} b5 {(b7-b5 Rf1-f2 Rh8-h5 e4-e5 a7-a5 Rf2-h2 Kc7-c6 Kc1-b2
Be6-d5 Rd2-d3 Bd5-e6) +0.57/11 3} 33. Rff2 {(f1f2 h8e8 f4f5 e6c4 f2h2 e8e4
f5g6) -0.13/7 2} a5 {(a7-a5 e4-e5 Kc7-c6 Rf2-h2 Rh8-h4 Rd2-d4 Rh4-h5 Kc1-c2
Be6-d5 a3-a4 b5xa4 Rd4xa4) +0.57/11 3} 34. Kc2 {(f4f5 g6f5 e4f5 e6d7 f5f6
h8g8 f2e2) -0.09/7 3} Rh5 {(Rh8-h5 e4-e5 f7-f6 e5xf6 Rh5-f5 Kc2-d3 Rf5xf6
Kd3-d4 Be6-c4 Kd4-e5 Rf6-f5+ Ke5-e4 Kc7-c6) +0.67/12 2} 35. Kd3 {(c2d3 c7c6
d3d4 h5c5 d2d3 c5c4 d4e5 c6c5) -0.16/7 3} g5 {(g6-g5 f4xg5 Rh5xg5 Kd3-d4
Kc7-d6 Rd2-e2 Rg5-g4 Rf2-h2 Rg4-h4 Re2-b2 Rh4-h5 Rh2-f2) +0.68/12 3} 36.
fxg5 {(f4g5 h5g5 d3d4 c7d6 d2d3 g5g2 e4e5 d6d7 f2d2) -0.04/8 2} Rxg5
{(Rh5xg5 Kd3-d4 Kc7-c6 Rf2-h2 Rg5-g1 Rd2-f2 Rg1-d1+ Kd4-e5 a5-a4 Rf2-f6
Rd1-d3 Rh2-c2 Rd3-e3) +0.72/12 2} 37. Kd4 {(d3d4 c7d6 d2e2 g5e5 f2h2 e5g5
e2d2) -0.03/7 3} Kd6 {(Kc7-d6 Rd2-b2 Rg5-h5 Rb2-b1 Rh5-c5 Rf2-h2 a5-a4
Rh2-b2 Be6-d7 Rb2-h2 Bd7-e6) +0.69/11 2} 38. Rh2 {(f2h2 g5c5 d2b2 c5c4 d4d3
e6d7 h2f2 d6e6) -0.08/7 3} Rg1 {(Rg5-g1 Rd2-d3 Rg1-a1 e4-e5+ Kd6-c6 Rd3xh3
Be6xh3 Rh2xh3 Ra1xa3 Rh3-h6+ Kc6-d7 Rh6-f6 Kd7-e7 c3-c4) +1.55/12 2} 39.
Rb2 {(d2b2 d6c6 b2f2 g1d1 d4e5 d1d3 f2c2 c6c5) -0.18/7 2} Kc6 {(Kd6-c6
Rb2-f2 Rg1-d1+ Kd4-e5 Kc6-c5 Rf2-f6 Rd1-d3 Rh2-c2 Kc5-c4 Rf6-f2 a5-a4
Rf2-d2 Rd3xd2 Rc2xd2 Kc4xc3) +1.65/13 3} 40. Rbf2 {(b2f2 g1d1 d4e5 c6c5
f2f6 d1a1 f6e6 f7e6 h2h3 a1a3 e5e6) -0.20/7 2} Rd1+ {(Rg1-d1+) +1.66/12 2}
41. Ke5 {(d4e5 c6c5 f2f6 d1d3 h2c2 c5c4 f6f1 d3c3 c2c3 c4c3) -0.76/7 3} Kc5
{(Kc6-c5 Rf2-d2 Rd1-a1 Rd2-d6 Ra1xa3 Rd6xe6 f7xe6 Rh2xh3 Kc5-c4 Ke5xe6
Ra3xc3 Rh3-h7 b5-b4 e4-e5) +1.81/14 3} 42. Rf6 {(f2f6 d1d3 h2c2 c5c4 f6f2
d3c3 c2c3 c4c3 f2f3) -0.76/8 3} Rd3 {(Rd1-d3 Rh2-c2 Kc5-c4 Rc2-c1 Rd3xc3
Rc1xc3+ Kc4xc3 Ke5-d6 b5-b4 a3xb4 a5xb4 e4-e5 b4-b3 Rf6xe6 f7xe6 Kd6xe6)
+2.30/15 2} 43. Rc2 {(h2c2 c5c4 f6f1 c4b3 c2h2 a5a4 f1a1 b3c3) -0.84/8 3}
Kc4 {(Kc5-c4 Rf6-f2 Rd3xc3 Rc2xc3+ Kc4xc3 Rf2-f3+ Kc3-c4 Ke5-f4 b5-b4 a3xb4
a5xb4 Rf3-f2) +2.43/14 3} 44. Rf1 {(f6f1 d3c3 c2c3 c4c3 f1g1 b5b4 a3b4 a5b4
g1g7) -0.92/8 3} Rxc3 {(Rd3xc3 Rf1-f2 Rc3xc2 Rf2xc2+ Kc4-d3 Rc2-c6 b5-b4
a3xb4 a5xb4 Rc6-d6+ Kd3-e3 Rd6-d1 b4-b3) +2.46/13 3} 45. Rxc3+ {(c2c3 c4c3
f1b1 b5b4 a3b4 a5b4 b1c1 c3d3 c1d1 d3c4 d1d4) -1.22/8 2} Kxc3 {(Kc4xc3
Rf1-f3+ Kc3-c4 Rf3-f1 b5-b4 a3xb4 a5xb4 Rf1-c1+ Kc4-d3 Rc1-f1 b4-b3 Rf1-f2
Kd3-c3 Rf2-f3+) +2.52/13 3} 46. Kf4 {(e5f4 b5b4 a3b4 a5b4 f4e5 c3d2 f1f2
d2d3 f2h2) -1.27/8 3} b4 {(b5-b4 a3xb4 a5xb4 Kf4-e3 b4-b3 Rf1-c1+ Kc3-b2
Rc1-h1 Kb2-a2 Ke3-d3 b3-b2 Kd3-c2 h3-h2 e4-e5 Be6-d5) +2.71/14 3} 47. axb4
{(a3b4 a5b4 f4e5 b4b3 f1f3 c3d2 f3f2 d2e3 f2h2 e3d3) -1.49/8 2} axb4
{(a5xb4 Kf4-e3 b4-b3 Rf1-c1+ Kc3-b2 Ke3-d2 Kb2-a3 Rc1-a1+ Ka3-b4 Ra1-b1
Kb4-c4 Kd2-e3 h3-h2 Rb1-c1+ Kc4-b5 e4-e5 b3-b2) +2.78/14 2} 48. Ke5 {(f4e5
b4b3 f1f3 c3c2 f3f2 c2d3 f2f3 d3e2 f3g3 b3b2 g3g1) -1.56/8 2} b3 {(b4-b3
Rf1-f3+ Kc3-b2 Ke5-d4 Kb2-a3 Rf3-f1 b3-b2 e4-e5 h3-h2 Rf1-h1 Be6-a2 Rh1-d1
b2-b1Q Rd1xb1 Ba2xb1) +5.14/14 2} 49. Rf3+ {(f1f3 c3c2 f3f2 c2d3 e5f4 d3c3
f2f3 c3d4 f3f2 f7f6 f2d2) -1.67/8 3} Kb2 {(Kc3-b2) +5.35/13 3} 50. Kd4
{(e5d4 b2a3 e4e5 h3h2 f3f1 b3b2 f1b1 a3b3) -1.68/8 2} Ka3 {(Kb2-a3)
+5.45/13 2} 51. Rf1 {(e4e5 h3h2 f3f1 b3b2 f1h1 e6f5 e5e6 f7e6) -2.80/8 2}
b2 {(b3-b2 Kd4-e3 Ka3-a2 Ke3-f2 b2-b1Q Rf1xb1 Ka2xb1 Kf2-g3 Kb1-c2 Kg3-f3
Kc2-c3 Kf3-g3 Kc3-d4) +5.67/14 3} 52. Ke5 {(d4e5 e6a2 e5f4 f7f6 f4g3 b2b1q
f1b1 a2b1 g3h3 b1e4) -4.33/7 3} Ka2 {(Ka3-a2 Ke5-f4 b2-b1Q Rf1xb1 Ka2xb1
Kf4-g3 Kb1-c2 Kg3-f2 Kc2-d3 Kf2-f3 Kd3-d4 e4-e5 Kd4xe5 Kf3-g3 f7-f6)
+7.37/15 3} 53. Kf4 {(e5f4 b2b1q f1b1 a2b1 f4f3 b1c2 f3g3 c2d3 g3f4)
-4.81/9 2} b1=Q {(b2-b1Q Rf1xb1 Ka2xb1 Kf4-g3 Kb1-c2 Kg3-f3 Kc2-c3 Kf3-f2
Kc3-d3 Kf2-f3 f7-f6 Kf3-f2 Kd3xe4 Kf2-g3 Ke4-e5) +7.37/15 2} 54. Rxb1
{(f1b1 a2b1 f4g3 b1c2 e4e5 c2d3 g3f3 h3h2 f3g2) -5.28/9 2} Kxb1 {(Ka2xb1
Kf4-g3 Kb1-c2 Kg3-f3 Kc2-d3 e4-e5 Kd3-d4 Kf3-f2 Kd4xe5 Kf2-g3 Be6-d7 Kg3-h2
Bd7-g4 Kh2-g3 f7-f5 Kg3-f2 f5-f4) +7.77/17 3} 55. Kg3 {(f4g3 b1c2 e4e5 c2d3
g3f3 d3d4 f3f2 d4e5 f2g3 f7f6) -6.42/10 3} Kc2 {(Kb1-c2 Kg3-f2 Kc2-d3 e4-e5
Kd3-d4 Kf2-f3 Kd4xe5 Kf3-g3 Be6-g4 Kg3-h2 f7-f5 Kh2-g1 f5-f4 Kg1-f2 Ke5-d5
Kf2-f1 f4-f3) +8.09/17 2} 56. e5 {(e4e5 c2d3 g3f3 d3d4 f3f2 d4e5 f2g3 f7f6
g3f3 f6f5) -6.55/10 3} Kc3 {(Kc2-c3 Kg3-f3 Kc3-d4 Kf3-f2 Kd4xe5 Kf2-g3
Be6-g4 Kg3xg4 h3-h2 Kg4-f3 h2-h1Q+ Kf3-e2 f7-f5 Ke2-d2 f5-f4 Kd2-c2 f4-f3
Kc2-c3) +11.32/17 2} 57. Kf3 {(g3f3 c3d4 f3f2 d4e5 f2g3 f7f6 g3h2 e5f4
h2g1) -6.52/9 2} Kd4 {(Kc3-d4 Kf3-f2 Kd4xe5 Kf2-f1 f7-f5 Kf1-g1 f5-f4
Kg1-f2 Be6-g4 Kf2-f1 f4-f3 Kf1-f2 h3-h2 Kf2-g3 f3-f2 Kg3xg4 h2-h1Q)
+11.75/17 2} 58. Kf2 {(f3f2 d4e5 f2g3 e6g4 g3h2 f7f5 h2g1 f5f4 g1f2 f4f3)
-7.06/10 3} Kxe5 {(Kd4xe5 Kf2-g3 Ke5-e4 Kg3-h2 Ke4-f4 Kh2-g1 Kf4-g3 Kg1-f1
h3-h2 Kf1-e2 h2-h1Q Ke2-e3 f7-f5 Ke3-d3 f5-f4 Kd3-c2 f4-f3 Kc2-c3)
+14.50/18 2} 59. Kf3 {(f2g3 e6g4 g3h2 f7f5 h2h1 f5f4 h1g1 f4f3 g1f2)
-7.06/9 3} f5 {(f7-f5 Kf3-g3 f5-f4+ Kg3-f2 Be6-d5 Kf2-g1 f4-f3 Kg1-h2 f3-f2
Kh2xh3 f2-f1Q+ Kh3-h4 Qf1-g2 Kh4-h5 Qg2-h3+ Kh5-g5 Qh3-g2+) +13.29/16 2}
60. Kf2 {(f3f2 e5f4 f2f1 e6d5 f1g1 f4g3 g1f1 h3h2 f1e2 h2h1q) -13.46/10 3}
Kf4 {(Ke5-f4 Kf2-f1 Kf4-f3 Kf1-g1 Kf3-g3 Kg1-f1 h3-h2 Kf1-e2 h2-h1Q Ke2-d2)
+18.16/16 3} 61. Ke2 {(f2f1 e6c4 f1f2 c4d3 f2g1 f4g3 g1h1 d3e4 h1g1 h3h2
g1f1 h2h1q) -13.66/9 2} h2 {(h3-h2 Ke2-d3 h2-h1Q Kd3-c3 Qh1-e1+ Kc3-b2
Qe1-d1 Kb2-c3 Qd1-b3+ Kc3-d2 Qb3-b2+) +199.77/15} 62. Kd3 {(e2d3 f4e5 d3d2
h2h1q d2c3 f5f4 c3d3 f4f3) -14.07/8 2} h1=Q {(h2-h1Q Kd3-d2 Qh1-d5+)
+199.77/5} 63. Kd2 {(d3d2 f4e5 d2d3 f5f4 d3c3 h1h3 c3b4 f4f3) -14.17/7 3}
Qd5+ {(Qh1-d5+) +199.79/2} 64. Kc3 {(d2c3 f4e5 c3b4 f5f4 b4a4 d5c4 a4a5
f4f3) -14.27/6 3} Qb3+ {(Qd5-b3+) +199.85/2} 65. Kd2 {(c3d2 b3b2 d2d3 b2c1
d3e2 e6c4 e2f2 c1f1) -M4/6} Qb2+ {(Qb3-b2+) +199.87/2} 66. Kd3 {(d2d3 b2c1
d3e2 e6c4 e2f2 c1f1) -M3/5} Qb3+ {(Qb2-b3+) +199.85/2} 67. Kd2 {(d3d2)
0.00/23 3} Qe3+ {(Qb3-e3+ Kd2-c2 Qe3-b3+) +199.79/3} 68. Kc2 {(d2c2 f4e5
c2b2 e3d2 b2b1 f5f4 b1a1 f4f3) -14.57/6 3} Qb3+ {(Qe3-b3+) +199.81/2} 69.
Kd2 {(c2d2) 0.00/32 3-fold repetition} 1/2-1/2
[/pgn]

I set up the position from the command prompt and got a different outcome. The mate is discovered (great) and there is a bit of shuffling around but at least the outcome is mate:

Code: Select all

Ian's Low Memory Chess Program (plankton)
Version 8.7.6, 10/7/2020
Copyright 2020 Ian Mitchell
With late move reductions!
With history heuristic!
With evaluation cache!
With null moves!
With hash table!
With tapered eval!
With razoring!
With reverse pruning!
With futility pruning!

"help" displays a list of commands.

plankton> fen 8/8/4b3/5p2/5k2/7p/4K3/8 b - - 3 61
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . p 3
2 . . . . K . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Black to move.
plankton> st 60
Search time: 60000ms
plankton> go
ply  mv   time     nodes score pv
  1   0      0        15   761   1 h3h2
  2   0      0        53  1422   3 h3h2 e2d3 (h2h1q)
  3   0     16       116  1422   3 h3h2 e2d3 h2h1q
  4   0     16       187  1411   5 h3h2 e2d3 h2h1q d3d4
  5   0     16       324  1416   6 h3h2 e2d3 h2h1q d3d4 e6d5
  6   0     16       968  1438   8 h3h2 e2d3 h2h1q d3d4 h1h8 d4d3 (f4e5)
  7   0     16      3624  1446   9 h3h2 e2d3 h2h1q d3d4 h1d1 d4c3 f4e5 (c3b2)
  8   0     16      9621  1461  11 h3h2 e2d3 h2h1q d3d2 f4e5 d2c2 h1e4 c2c3 (f5f4)
  9   0     31     31375  1471  12 h3h2 e2d3 h2h1q d3d4 h1d1 d4c5 f4e5 c5b5 d1d5 (b5b4 f5f4)
 10   0     47     52354  1474  13 h3h2 e2d3 h2h1q d3d4 h1d1 d4c5 f4e5 c5b4 f5f4 b4c3 (f4f3)
 11   0    156    246491  1479  14 h3h2 e2d3 h2h1q d3c3 f4e5 c3d3 f5f4 d3d2 f4f3 d2e3 e6d5
 12   0    391    710645  1488  18 h3h2 e2d3 h2h1q d3d2 f4e5 d2e2 f5f4 e2f2
 13   0    656   1235803  2169  19 h3h2 e2d3 h2h1q d3d2 f4e5 d2e2 f5f4 e2f2 f4f3 f2e3 h1g1 e3d2 f3f2 (d2c2 f2f1q)
 14   0   1109   2058831  2169  19 h3h2 e2d3 h2h1q d3d2 f4e5 d2e2 f5f4 e2f2 f4f3 f2e3 h1g1 e3d2 f3f2 d2c2 (f2f1q)
 15   0   1281   2292098  2169  20 h3h2 e2d3 h2h1q d3d2 f4e5 d2e2 f5f4 e2f2 f4f3 f2e3 h1g1 e3d2 f3f2 d2c2 f2f1q (c2b2)
 16   0   3531   6322904  2169  23 h3h2 e2d3 h2h1q d3d2 f4e5 d2e2 f5f4 e2d3 f4f3 d3c3 h1g2 c3b4 g2g4 b4c3 f3f2 c3d2 (f2f1q)
 17   0  12594  22157818 19985  27 h3h2 e2d3 h2h1q d3d2 f4f3 d2c3 h1e1 c3c2 f3e4 c2b2 e1d2 b2b1 e4f4
nreps: 42106
nhash: 3509812
hashorder: 1157361
razor: 170721
prune: 3323597
hist: 57849
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 . . . . K . . p 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: h3h2
plankton> e2d3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . . . . . . . p 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1   2      0        18  1422   1 h2h1q
  2   2      0        43  1411   2 h2h1q d3d4
  3   2      0       116  1416   4 h2h1q d3d4 e6d5
  4   2      0       809  1481   6 h2h1q d3d4 h1b1
  5   2      0      2419 19981   7 h2h1q d3d4 h1d5 d4c3 d5b3
nreps: 3
nhash: 157
hashorder: 212
razor: 34
prune: 199
hist: 12
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . . . . . . . . 2
1 . . . . . . . q 1
  A B C D E F G H

Computer's move: h2h1q
plankton> d3d2
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 . . . K . . . . 2
1 . . . . . . . q 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1   4      0        36  1442   1 f4e5
  2   4      0       204  1442   3 h1d5 d2c2 (f4e5)
  3   4      0      2242  1461   5 f4e5 d2d3 f5f4
  4   4      0      2654  1461   5 f4e5 d2c2 f5f4 c2c3
  5   4      0      9753 19975   9 h1d5 d2e1 d5e4 e1d2 e4e3 (d2c2 e3b3)
nreps: 16
nhash: 569
hashorder: 683
razor: 79
prune: 345
hist: 20
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . q . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 . . . K . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: h1d5, check!
plankton> d2c3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . q . p . . 5
4 . . . . . k . . 4
3 . . K . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1   6      0        33  1438   2 f4e5
  2   6     16       263 19985   3 d5b3
nreps: 0
nhash: 4
hashorder: 15
razor: 3
prune: 9
hist: 0
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . q K . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: d5b3, check!
plankton> c3d2
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . q . . . . . . 3
2 . . . K . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1   8      0        33  1442   1 f4e5
  2   8      0       119 19987   3 b3b2
nreps: 1
nhash: 10
hashorder: 7
razor: 0
prune: 4
hist: 0
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 . q . K . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: b3b2, check!
plankton> d2d3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . q . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  10      0        37  1438   1 f4e5
  2  10      0       287  1442   3 b2a3 d3c2 (f4e5)
  3  10     16      1269  2177   5 b2b1 d3c3 b1c1
  4  10     16      1478 19979   6 b2b1 d3c3 b1e1 c3d3 (e1d1)
nreps: 11
nhash: 145
hashorder: 141
razor: 22
prune: 168
hist: 10
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . . . . . . . . 2
1 . q . . . . . . 1
  A B C D E F G H

Computer's move: b2b1, check!
plankton> d3d4
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . K . k . . 4
3 . . . . . . . . 3
2 . . . . . . . . 2
1 . q . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  12      0        32  1411   2 b1b6
  2  12      0        63 19983   1 b1b6
nreps: 0
nhash: 27
hashorder: 1
razor: 0
prune: 3
hist: 0
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . q . . b . . . 6
5 . . . . . p . . 5
4 . . . K . k . . 4
3 . . . . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: b1b6, check!
plankton> d4d3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . q . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  14      0        33  1438   1 f4e5
  2  14      0       352 19979   3 b6e3
nreps: 2
nhash: 11
hashorder: 13
razor: 1
prune: 6
hist: 0
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K q . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: b6e3, check!
plankton> d3c2
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . q . . . 3
2 . . K . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  16      0        34  1442   1 f4e5
  2  16      0       197  1446   3 f4e5 c2b2
  3  16      0      2094  1470   5 e3e2 c2b1 e2d2 (b1a1)
  4  16     15      3644  1486   7 e3e2 c2b1 e2d2 b1a1 (f4e5)
  5  16     15      6305 19979   9 e3e2 c2c3 e2c4
nreps: 13
nhash: 566
hashorder: 418
razor: 27
prune: 192
hist: 14
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 . . K . q . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: e3e2, check!
plankton> c2c3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . K . . . . . 3
2 . . . . q . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  18      0        36  1438   2 f4e5
  2  18      0        72 19981   1 e2c4
nreps: 0
nhash: 31
hashorder: 1
razor: 0
prune: 4
hist: 0
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . q . . k . . 4
3 . . K . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: e2c4, check!
plankton> c3d2
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . q . . k . . 4
3 . . . . . . . . 3
2 . . . K . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  20      0        31  1442   1 f4e5
  2  20      0       167 19983   3 c4a2
nreps: 1
nhash: 5
hashorder: 12
razor: 3
prune: 6
hist: 0
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 q . . K . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: c4a2, check!
plankton> d2d3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 q . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  22      0        31  1438   1 f4e5
  2  22      0       149  1442   3 a2a3
  3  22      0      1388  1461   5 f4e5 d3c3 f5f4
  4  22      0      1832  1466   6 f4e5 d3e3 f5f4 e3f3 (e6d5)
  5  22      0      2854 19985   8 f4e5 d3e3 f5f4 e3d3 a2b3
nreps: 13
nhash: 243
hashorder: 244
razor: 38
prune: 168
hist: 12
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . k p . . 5
4 . . . . . . . . 4
3 . . . K . . . . 3
2 q . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: f4e5
plankton> d3c3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . k p . . 5
4 . . . . . . . . 4
3 . . K . . . . . 3
2 q . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  24     15        32  1461   2 f5f4
  2  24     15       115  1511   3 a2e2
  3  24     15       422 19995   3 e6c4 c3b4
nreps: 1
nhash: 153
hashorder: 32
razor: 0
prune: 82
hist: 9
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . . . . . 6
5 . . . . k p . . 5
4 . . b . . . . . 4
3 . . K . . . . . 3
2 q . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: e6c4
plankton> c3b4
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . . . . . 6
5 . . . . k p . . 5
4 . K b . . . . . 4
3 . . . . . . . . 3
2 q . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  26      0        35  1471   2 f5f4
  2  26      0       107 19997   2 a2b3
nreps: 0
nhash: 2
hashorder: 20
razor: 5
prune: 0
hist: 0
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . . . . . 6
5 . . . . k p . . 5
4 . K b . . . . . 4
3 . q . . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: a2b3, check!
plankton> b4a5
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . . . . . 6
5 K . . . k p . . 5
4 . . b . . . . . 4
3 . q . . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1  28      0        36  1479   2 f5f4
  2  28      0        80 19999   2 b3b5
nreps: 0
nhash: 14
hashorder: 5
razor: 1
prune: 2
hist: 0
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . . . . . 6
5 K q . . k p . . 5
4 . . b . . . . . 4
3 . . . . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: b3b5, check!
0-1 {Black mates}
plankton>

It seems like depending on what's in the HT it is struggling to make the fast mate. What can I do to avoid that?

Many thanks, Ian

hgm · Post by **hgm** » Sat Jul 11, 2020 8:25 am

If I believe the opponent's scores, your mating distances are wrong. At least, I assume that your mate score is 200. When TSCP says -M4, you get 199.87 on the move afterter that. Which would mean mate (or King capture) in 13 ply = 6 moves, while it should have been in 4. This is suspect.

What is also suspect is that you reach a very low depth for these moves. You should iterate at least to the mating distance. It seems you stop iterating just when you reach any mate score, without the depth being large enough to guarantee it is the fastest mate.

ianm · Post by **ianm** » Sat Jul 11, 2020 11:35 am

Yes of course! I've been exiting the iterative deepening search when a mate score is detected because that was in place before I added the HT. I didn't think of it because the HT can be enabled or disabled. Here is the result now:

Code: Select all

Ian's Low Memory Chess Program (plankton)
Version 8.7.7, 11/7/2020
Copyright 2020 Ian Mitchell
With late move reductions!
With history heuristic!
With evaluation cache!
With null moves!
With hash table!
With tapered eval!
With razoring!
With reverse pruning!
With futility pruning!

"help" displays a list of commands.

plankton> fen 8/8/4b3/5p2/5k2/7p/4K3/8 b - - 3 61
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . p 3
2 . . . . K . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Black to move.
plankton> st 20
Search time: 20000ms
plankton> go
ply  mv   time     nodes score pv
  1   0      0        15   761   1 h3h2
  2   0      0        53  1422   3 h3h2 e2d3 (h2h1q)
  3   0      0       116  1422   3 h3h2 e2d3 h2h1q
  4   0      0       188  1411   5 h3h2 e2d3 h2h1q d3d4
  5   0      0       327  1416   6 h3h2 e2d3 h2h1q d3d4 e6d5
  6   0      0       972  1438   8 h3h2 e2d3 h2h1q d3d4 h1h8 d4d3 (f4e5)
  7   0     16      3630  1446   9 h3h2 e2d3 h2h1q d3d4 h1d1 d4c3 f4e5 (c3b2)
  8   0     16      9559  1461  11 h3h2 e2d3 h2h1q d3d2 f4e5 d2c2 h1e4 c2c3 (f5f4)
  9   0     32     32095  1471  12 h3h2 e2d3 h2h1q d3d4 h1d1 d4c5 f4e5 c5b5 d1d5 (b5b4 f5f4)
 10   0     47     53045  1484  14 h3h2 e2d3 h2h1q d3d4 h1d1 d4c5 f4e5 c5b4 f5f4 b4c3 (f4f3)
 11   0    141    220660  1489  14 h3h2 e2d3 h2h1q d3c3 f4e5 c3d3 f5f4 d3d2 f4f3 d2e3 e6d5
 12   0    360    627872  1507  18 h3h2 e2d3 h2h1q d3c3 h1e1 c3c2 f4e5 c2d3 f5f4 d3c2 f4f3 c2d3 (f3f2)
 13   0    735   1328629  2169  20 h3h2 e2d3 h2h1q d3c3 h1e1 c3c2 f4e5 c2d3 f5f4 d3c2 f4f3 c2d3 f3f2 (d3c2 f2f1q)
 14   0   1141   2026125  2169  20 h3h2 e2d3 h2h1q d3c3 h1e1 c3c2 f4e5 c2d3 f5f4 d3c2 f4f3 c2d3 f3f2 d3c2 (f2f1q)
 15   0   2422   4127393 19983  22 h3h2 e2d3 h2h1q d3d2 h1e4 d2c3 e4e1
 16   0   7188  12753460 19983  24 h3h2 e2d3 h2h1q d3d2 h1b1 d2c3 b1e1
nreps: 78722
nhash: 6330725
hashorder: 2055357
razor: 295241
prune: 6583418
hist: 60000
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 . . . . K . . p 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: h3h2
plankton> e2d3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . . . . . . . p 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1   2      0        18  1422   1 h2h1q
  2   2      0        44  1411   2 h2h1q d3d4
  3   2      0       119  1416   4 h2h1q d3d4 e6d5
  4   2      0       663  1438   6 h2h1q d3d2 f4e5 d2c3
  5   2      0      2449  1461   7 h2h1q d3d2 f4e5 d2c3 f5f4
  6   2      0      4086  1461   7 h2h1q d3d2 f4e5 d2c2 h1e4 c2c3 (f5f4)
  7   2     16     13086  1827   9 h2h1q d3d2 e6b3 d2c3 h1f3
  8   2     16     23482  1827  13 h2h1q d3d2 e6b3 d2c3 h1f3
  9   2     16     25571  1827  13 h2h1q d3d2 e6b3 d2c3 h1f3
 10   2     31     27824  1827  14 h2h1q d3d2 e6b3 d2c3 h1f3
 11   2     31     41830  2170  14 h2h1q d3d2 h1e4 d2c3 e4e5 c3c2 e5e2
 12   2     78    101668 19973  18 h2h1q d3d2 h1b1 d2c3 b1c1 c3b4 c1b1
 13   2    188    258902 19983  19 h2h1q d3d2 h1a1 d2c2 a1e1 c2d3 f4f3
 14   2    344    493045 19987  20 h2h1q d3d2 h1a1 d2e2 a1c1 e2f2 c1e3 f2f1 e6c4 f1g2 e3g3 g2h1 c4d5
 15   2   1485   2531586 19989  24 h2h1q d3d2 h1a1 d2e2 a1c1 e2f2 e6d5 f2e2 d5c4 e2f2 c1f1
 16   2   8141  14235412 19989  24 h2h1q d3d2 h1a1 d2e2 a1c1 e2f2 e6d5 f2e2 d5c4 e2f2 c1f1
nreps: 97856
nhash: 7058963
hashorder: 2001621
razor: 316728
prune: 10697815
hist: 60000
curo: 0

hash table usage: 0%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . . . . . . . . 2
1 . . . . . . . q 1
  A B C D E F G H

Computer's move: h2h1q
plankton> d3d2
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 . . . K . . . . 2
1 . . . . . . . q 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1   4      0        36  1442   1 f4e5
  2   4     15       215  1438   3 f4e5 d2c3
  3   4     15      1827  1461   5 f4e5 d2c3 f5f4
  4   4     15      2733  1461   5 f4e5 d2c2 f5f4 c2c3
  5   4     15      4498  1484   7 f4e5 d2c2 f5f4 c2c3 f4f3
  6   4     15      8185  1827   8 e6b3 d2c3 h1f3
  7   4     15      9111  1827  10 e6b3 d2c3 h1f3
  8   4     15     10330  1827  12 e6b3 d2c3 h1f3
  9   4     15     14773  1827  14 e6b3 d2c3 h1f3
 10   4     47     49078 19985  16 h1b1 d2e2 b1b2 e2d1 e6b3 d1e1 b2c1 e1f2 c1e3
 11   4     62     72426 19989  16 h1b1 d2e2 b1c1 e2f2 c1e3 f2f1 e6c4 f1g2 e3g3 g2h1 c4d5
 12   4     93    114663 19989  16 h1b1 d2e2 b1c1 e2f2 c1e3 f2f1 e6c4 f1g2 e3g3 g2h1 c4d5
 13   4    187    229317 19989  18 h1b1 d2c3 b1c1
 14   4    359    462343 19991  17 h1c6 d2e2 c6c1 e2f2 e6d5 f2e2 d5c4
 15   4    906   1289007 19993  22 h1c6 d2e2 c6c2 e2f1 f4f3 f1e1 c2c1
 16   4   4047   6021092 19993  24 h1c6 d2e2 c6c2 e2f1 f4f3 f1e1 c2c1
 17   4  16859  24232235 19993  26 h1c6 d2e2 c6c2 e2f1 f4f3 f1e1 c2c1
nreps: 126776
nhash: 7091976
hashorder: 1796921
razor: 269342
prune: 13296087
hist: 60000
curo: 0

hash table usage: 1%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . q . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . . . . . . 3
2 . . . K . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: h1c6
plankton> d2d3
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . q . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1   6      0        35  1438   1 f4e5
  2   6      0        91 19987   2 c6d6
  3   6      0       546 19987   4 c6d6
  4   6      0       581 19987   1 c6d6
  5   6      0       616 19987   1 c6d6
  6   6      0      2496 19989   6 c6b5 d3c3 b5b3 c3d2 b3b2
  7   6     16      3608 19989   8 c6b5 d3c3 b5b3 c3d2 b3b2
  8   6     16      5857 19989  10 c6b5 d3c3 b5b3 c3d2 b3b2
  9   6     16     10698 19989  12 c6b5 d3c3 b5b3 c3d2 b3b2
 10   6     31     22720 19995  15 c6c1 d3e2 e6c4 e2f2 c1f1
 11   6     47     33063 19995  13 c6c1 d3e2 e6c4 e2f2 c1f1
 12   6     63     59288 19995  16 c6c1 d3e2 e6c4 e2f2 c1f1
 13   6    109    118943 19995  14 c6c1 d3e2 e6c4 e2f2 c1f1
 14   6    188    226152 19995  16 c6c1 d3e2 e6c4 e2f2 c1f1
 15   6    344    452612 19995  17 c6c1 d3e2 e6c4 e2f2 c1f1
 16   6    953   1249294 19995  20 c6c1 d3e2 e6c4 e2f2 c1f1
 17   6   8391  12107207 19995  26 c6c1 d3e2 e6c4 e2f2 c1f1
nreps: 148754
nhash: 8220125
hashorder: 1609675
razor: 261340
prune: 14674128
hist: 60000
curo: 0

hash table usage: 1%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . . . k . . 4
3 . . . K . . . . 3
2 . . . . . . . . 2
1 . . q . . . . . 1
  A B C D E F G H

Computer's move: c6c1
plankton> d3d4
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . . K . k . . 4
3 . . . . . . . . 3
2 . . . . . . . . 2
1 . . q . . . . . 1
  A B C D E F G H

ply  mv   time     nodes score pv
  1   8      0        32  1411   2 c1b1
  2   8      0        74 19999   2 c1c4
  3   8      0       209 19999   3 c1c4
  4   8      0       240 19999   2 c1c4
  5   8      0       271 19999   2 c1c4
  6   8      0       406 19999   3 c1c4
  7   8      0       543 19999   3 c1c4
  8   8      0       680 19999   3 c1c4
  9   8      0       817 19999   3 c1c4
 10   8     16      2035 19999   8 c1c4
 11   8     16      3157 19999   6 c1c4
 12   8     16      4317 19999   6 c1c4
 13   8     16      6282 19999   9 c1c4
 14   8     16     13714 19999  10 c1c4
 15   8     32     27011 19999  12 c1c4
 16   8     47     53678 19999  15 c1c4
 17   8    141    187695 19999  17 c1c4
 18   8   2860   3933395 19999  24 c1c4
 19   8  15063  20773721 19999  26 c1c4
nreps: 122111
nhash: 8195027
hashorder: 1295315
razor: 288404
prune: 16433200
hist: 60000
curo: 0

hash table usage: 2%
  A B C D E F G H
8 . . . . . . . . 8
7 . . . . . . . . 7
6 . . . . b . . . 6
5 . . . . . p . . 5
4 . . q K . k . . 4
3 . . . . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  A B C D E F G H

Computer's move: c1c4, check!
0-1 {Black mates}
plankton>

is there a way now to exit the iterative deepening loop early when mate is detected?

Thanks again HG!

hgm · Post by **hgm** » Sat Jul 11, 2020 1:01 pm

Well, you could stop iterating when you reach the depth that corresponds to the mate score. If you do a lot of pruning, that still doesn't guarantee you have seen the fastest mate, though. A strongly reduced branch could lead to a quicker mate that it hasn't seen yet. So you can do a few ply extra to be sure.

It wouldn't give you any extra Elo, of course.

If you do mate-distance pruning, the tree stays so small when you approach the mate that the search deepends to the maximum depth in a flash anyway. I guess with the method you use (correcting the mate score with the ply depth in the leaves) you would have to explicitly implement that (e.g. fail low without searching any moves if even capture of a King cannot rise the score above alpha).

ianm · Post by **ianm** » Sun Jul 12, 2020 7:56 am

I think I'll just have a check for mate-in-one. Not fussed about taking time to get to the fastest mate but when a mate in one is found better to stop now than waste time at that point.

Code: Select all

if (abs(score) >= (MAX_VALUE-1)) break;

Correct way to store and extract mate scores

Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores

Re: Correct way to store and extract mate scores