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Subject: Re: Strange behaviour of my new engine

Author: Anthony Cozzie

Date: 06:23:25 08/02/04

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On August 01, 2004 at 12:54:03, Steffen Basting wrote:

>Hi Gerd!
>
>Thanks for replying!
>
>>Mate in 4 should be independent from search depth.
>>Isn't the game over after Rh8#?
>
>Yes, of course :-)
>
>>Seems that you don't terminate your PVs correctly.
>
>I've just fixed this. It now says:
>0.00s   1=      315        187    f4f1
>0.00s   2=      1926       148    f4f1 d7c7
>0.04s   3=      23053      131    f4f2 e6g4 e1e8 a8e8 d4a7
>0.20s   4=      93395      89     e1d1 f7f6 g5h4 a8c8
>0.87s   5=      515342     97     f4f1 f7f6 g5f4 e6f5 e1c1
>2.48s   6=      1452346    68     f4f1 e6f5 c2c3 e8e1 f1e1 a8e8 e1d1 e8e2
>6.68s   7=      4129525    70     f4f2 e6g4 e1f1 f7f6 g5f4 d7e6 f4c7
>8.57s   8=      5185655    120    f4f2 e6g4 e1f1 f7f6 g5f4 g6g5 f4d6 d7d6
>8.58s   8+      5195575    370    f4f2 e6g4 e1f1 f7f6 g5f4 g6g5 f4d6 d7d6
>8.60s   8+      5205409    870    f4f2 e6g4 e1f1 f7f6 g5f4 g6g5 f4d6 d7d6
>8.73s   8++     5296335    #4     d4g7 g8g7 g5f6 g7g8 f4h4 e6f5 h4h8 #
>9.09s   9=      5529524    #4     d4g7 g8g7 g5f6 g7g8 f4h4 e6f5 h4h8 #
>9.64s   10=     5896253    #4     d4g7 g8g7 g5f6 g7g8 f4h4 e6f5 h4h8 #
>11.86s  11=     7560467    #4     d4g7 g8g7 g5f6 g7g8 f4h4 e6f5 h4h8 #
>19.04s  12=     12961258           #4     d4g7 g8g7 g5f6 g7g8 f4h4 e6f5 h4h8 #
>34.34s  13=     23696937           #4     d4g7 g8g7 g5f6 g7g8 f4h4 e6f5 h4h8 #
>
>>How to translate your mate scores?
>
>When a mate occurs, I return 20000+depth so that "short" mates are preferred.
>But you were right, I forgot to set the counter to 0 then, this caused those
>strange lines.
>
>>1.bugs
>
>Yeah, there are probably plenty of them :-)
>
>>2.better eval
>
>Does eval have such a positive effect on depth / node ratio?
>
>>3.carefull with R==3 near the leaves, checks in qsearch?
>
>Yes, R=3 seems to be dangerous sometimes. I now use R=2 when the depth is
>low. I don't use checks in qsearch (yet)...
>
>>4.SEE or more sophisticated move ordering, checks, putting pieces enprise,
>>  at interior nodes one may use more expensive move scoring/sorting.
>>5.hashing score and bounds or flags as well.
>>6.fractional extension/reductions.
>>7.tuning.
>
>4-7 will be done after I've finished with 1 ;-)
>
>Thanks again,
>Steffen

I think eval has two effects on move ordering.  First, a good eval decreases
your flip-rate, which helps with parallel search and reduces the amount of time
the engine "doubts", which is expensive.  However, because it increases the
granularity it also reduces the number of "=" beta cutoffs.

Unfortunately I think the second effect tends to dominate.

anthony



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