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Subject: Re: Slow EGTBs - test position

Author: David Rasmussen

Date: 12:37:07 01/16/03

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[D]8/4n3/1k6/1p4p1/1P4P1/1K6/3B4/8 w - - 0 1

In a position such as this, this is Chezzz _without_ EGTBs:

I'm thinking...
time         nodes depth    score  pv
00:00:00.19  146kn 09/12/14 +1.125 1. Bxg5 Ng6 2. Bf6 Kc6
                                   3. Kc3 Kd5 4. Kd2 Ke4
                                   5. Ke2 (146312)
00:00:00.25  191kn 09/14/15 ---------------------------------------------------
00:00:00.41  296kn 10/14/15 +1.085 1. Bxg5 Ng6 2. Bf6 Kc6
                                   3. Kc3 Kd5 4. Kd3 Ke6
                                   5. Bd4 Ne5+ 6. Bxe5 Kxe5 (296663)
00:00:00.55  391kn 10/15/16 ---------------------------------------------------
00:00:00.67  491kn 11/16/17 +1.085 1. Bxg5 Ng6 2. Bf6 Kc6
                                   3. Kc3 Kd5 4. Kd3 Ke6
                                   5. Bd4 Ne5+ 6. Bxe5 Kxe5 (491020)
00:00:00.91  677kn 11/17/18 ---------------------------------------------------
00:00:01.53 1150kn 12/17/19 +1.130 1. Bxg5 Ng6 2. Kc3 Ne5
                                   3. Bd8+ Kc6 4. g5 Kd5
                                   5. Bc7 Ng6 6. Kd3 Ke6
                                   7. Ke4 (1150376)
00:00:01.83 1393kn 12/18/19 ---------------------------------------------------
00:00:03.63 2787kn 13/20/21 +1.075 1. Bxg5 Nd5 2. Bd2 Kc6
                                   3. Kc2 Kd6 4. Kd3 Ke5
                                   5. g5 Ne7 6. Bc3+ Kd5
                                   7. Bd4 Ng6 (2787724)
00:00:04.49 3467kn 13/20/23 ---------------------------------------------------
00:00:06.83 5239kn 14/20/22 +1.040 1. Bxg5 Nd5 2. Bd2 Kc6
                                   3. Kc2 Kd6 4. Kd3 Ke5
                                   5. g5 Kf5 6. Kd4 Nc7
                                   7. Kc3 Ke4 (5239484)
00:00:07.85 6053kn 14/22/23 ---------------------------------------------------
00:00:15.24   11Mn 15/22/24 +0.855 1. Bxg5 Nd5 2. Bd2 Kc6
                                   3. Ka3 Kd6 4. Bg5 Kd7
                                   5. Kb3 Ke6 6. Bd8 Ke5
                                   7. g5 Kf5 8. Ka3 (11513787)
00:00:18.97   13Mn 15/23/25 ---------------------------------------------------
00:00:28.80   20Mn 16/24/27   1/11 1. Bxg5

        Time used: 00:00:30.00
        nps: 718426     nodes: 21559976 Q-nodes: 707976 (3%)
        move order: 94%
        hash probes: 8770930    hash hits: 5045831 (57%)        hash usage: 99%
        pawn hash probes: 9470211       pawn hash hits: 9469820 (99%)
        EGTB probes: 0
1. Bxg5

This is Chezzz _with_ EGTBs:

time         nodes depth    score  pv
00:00:00.22  139kn 09/12/14 +1.125 1. Bxg5 Ng6 2. Bf6 Kc6
                                   3. Kc3 Kd5 4. Kd2 Ke4
                                   5. Ke2 (139961)
00:00:00.29  184kn 09/14/15 ---------------------------------------------------
00:00:00.45  284kn 10/14/15 +1.085 1. Bxg5 Ng6 2. Bf6 Kc6
                                   3. Kc3 Kd5 4. Kd3 Ke6
                                   5. Bd4 Ne5+ 6. Bxe5 Kxe5 (284263)
00:00:00.58  370kn 10/15/17 ---------------------------------------------------
00:00:00.73  472kn 11/15/16 +1.085 1. Bxg5 Ng6 2. Bf6 Kc6
                                   3. Kc3 Kd5 4. Kd3 Ke6
                                   5. Bd4 Ne5+ 6. Bxe5 Kxe5 (472265)
00:00:01.00  650kn 11/17/19 ---------------------------------------------------
00:00:01.42  920kn 12/18/19 +1.130 1. Bxg5 Ng6 2. Kc3 Ne5
                                   3. Bd8+ Kc6 4. g5 Kd5
                                   5. Bc7 Ng6 6. Kd3 Ke6
                                   7. Ke4 (920316)
00:00:01.75 1149kn 12/18/19 ---------------------------------------------------
00:00:03.48 2310kn 13/20/21 +1.075 1. Bxg5 Nd5 2. Bd2 Kc6
                                   3. Kc2 Kd6 4. Kd3 Ke5
                                   5. g5 Ne7 6. Be3 Ng6
                                   7. Bd4+ Kd5 (2310354)
00:00:04.45 2971kn 13/20/21 ---------------------------------------------------
00:00:12.04 4334kn 14/20/23 +1.040 1. Bxg5 Nd5 2. Bd2 Kc6
                                   3. Kc2 Kd6 4. Kd3 Ke5
                                   5. g5 Kf5 6. Kd4 Nc7
                                   7. Kc3 Ke4 (4334933)
00:00:17.61 5058kn 14/21/23 ---------------------------------------------------
00:00:22.70 6143kn 15/20/22   1/11 1. Bxg5

        Time used: 00:00:30.00
        nps: 234538     nodes: 7038510  Q-nodes: 196510 (2%)
        move order: 95%
        hash probes: 3162813    hash hits: 2220367 (70%)        hash usage: 87%
        pawn hash probes: 2866265       pawn hash hits: 2865984 (99%)
        EGTB probes: 25055
1. Bxg5

That is quite a speed drop. What I don't understand is that during this search,
the disk is working like crazy. I only probe in the first 2 plys. There is 11
legal moves in the position, so that's roughly 100 positions. That can't take
that much activity to probe. And then I only probe within the iteration depth,
and only then if there have been a capture or a promotion, and only if the
number of pieces on the board is small enough (<= 5 for 3-5 man tables). In this
position, there is of course a capture now and then, and a promotion sometimes
too. But why this constant disk access? It really feels to me as if it's the
disk I/O that's killing me, and not because I have a slow disk, but because
there is far too much disk activity for some reason. And the reason isn't that I
probe too often due to a bug, because my probe numbers are like everybody elses.

You can see that I get about 25000 probes on a 30 second think on an Athlon XP
1800+. How much do you get?

/David



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