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Subject: Re: mate threat extension/null move

Author: Stuart Cracraft

Date: 16:32:27 09/29/04

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On September 29, 2004 at 18:52:45, Michael Henderson wrote:

>On September 29, 2004 at 17:29:57, Stuart Cracraft wrote:
>>On September 29, 2004 at 16:06:36, Uri Blass wrote:
>>>On September 29, 2004 at 14:51:16, Dan Honeycutt wrote:
>>>>On September 29, 2004 at 14:16:23, Stuart Cracraft wrote:
>>>>>WAC 141 takes me a shade over 24,000,000 nodes, a fully completed 7 ply search,
>>>>>to find Qxf4 with all the above improvements, still the same amount of
>>>>>time as without:
>>>>>Alpha=-1332 Beta=-532 Maxdepth=9999999 MaxTime=1410065407
>>>>> 1/11  g2f1  0.00 -953      945 g2f1 f4d5
>>>>>                                g2f1 f4d5
>>>>> 2/12  g2f1  0.01 -953     1653
>>>>>                                g2f1 f4d5 c1g5
>>>>> 3/12  g2f1  0.02 -953     5073
>>>>>                                g2f1 f4d5 c1g5 d5f6
>>>>> 4/20  g2f1  0.09 -953    19924
>>>>>                                g2f1 f4d5 b3d5 c6d5 c1c7 d6c7 f1g1
>>>>> 5/22  g2f1  0.71 -953   170357
>>>>>                                g2f1 b5b4 b3a4 f4d5 f6g5 d5e7
>>>>> 6/26  g2f1  2.85 -953   617222
>>>>>                                g2f1 b5b4 mtmt
>>>>> 7/32> g2f1 56.60 -553 13644478 g2f1 e8c8 c1b1 f4d5 b1e4 d6b4 f6e5 c7b6
>>>>>                                g2f1 e8c8 c1b1 f4d5 b1e4 d6b4
>>>>> 7/34  c1f4 97.33 5113 24161497 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7 f6e7
>>>>>                                c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1
>>>>> 8/34  c1f4 115.59 5113 27838968
>>>>>                                c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1
>>>>> 9/34> c1f4 197.37 5513 48705672
>>>>>                                c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 mtmt
>>>>> 9/... still searching
>>>>Doesn't look like the program has actually found Qxf4.  e8e6 is not the next
>>>>Dan H.
>>>The next move is not important
>>>Every move is losing and the question what is the next move in the program pv is
>>>dependent on extensions.
>>>It is clear that too many extensions were used because the program needs so many
>>>nodes to finish depth 7 and the selctive depth is too high(depth 7/34).
>>>I believe that the recapture extension that is used is bad if it helps to solve
>>>the problem at depth 7 with so many nodes but the only test to be sure is games.
>>I considered your last point as well and removed RECAP. The problem cannot
>>be resolved without it after 10+ minutes. With it, it solves at 95 seconds
>>at ply 7.
>>My main search escape-from-checks and quiescence escape-from-checks are
>>I do not search checking moves except in main search or unless a move
>>out of check in quiescence is a checking move.
>I think there is something wrong with your search.  -953 is too large of a
>losing score for g2f1, it should be around -100 to -300.  Can you post the
>complete variation that leads to this score? with Triangular array you can by
>not cutting off with a PV entry. h1d1 in the PV looks strange also.
>Recapture extension should not be helping you here, I believe.  I don't think
>even captures are hiding anything useful.

I measure in millipawns so -953 is just under a pawn down for Kf1
which is about the higher end of your range.

In the printout, the first line is the triangular array variation
and the line immediately under it is the walk-the-pv-in-hash variation.
So for ply 7:

>>>>> 7/34  c1f4 97.33 5113 24161497 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7 f6e7
>>>>>                                c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1

The c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7 is triangular array pv.

I have heard that said about recaptures but if I don't have it on it
fails. My recapture extension is:

#ifdef RECAP
  // Extend if a recapture
  if (!extended && histptr >= 2 && hist[histptr-1].cap != 0 &&
        hist[histptr-2].cap != 0 && hist[histptr-1].to == hist[histptr-2].to
#ifdef NEVER
        && ABS(hist[histptr-2].pc) == ABS(hist[histptr-1].cap)
        && ABS(hist[histptr-2].cap) == ABS(hist[histptr-1].cap)
    ) {


I don't have the NEVER on as that limits the recaptures too severely.
By just limiting to two captures by any pieces to the same square
in the last two moves, without regards to the piece or the material,
that RECAP is what gets me WAC 141 at all. If I don't have it or have
it in that exact way as above, I don't get WAC 141 at all. With it
I get WAC 141 with or without my mate-threat at the same time interval
of 95-97 seconds.


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