No mate threat extension in new Glaurung?

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Uri Blass
Posts: 8009
Joined: Wed Mar 08, 2006 11:37 pm
Location: Tel-Aviv Israel

No mate threat extension in new Glaurung?

Post by Uri Blass » Mon Jun 11, 2007 1:29 pm

I wonder if tord found mate threat extension counter productive or he simply did not try it:

From Glaurng's code:

Code: Select all

 Depth extension(Position& pos, Move m, bool pvNode,
                  bool check, bool singleReply, bool recapture) {
    Depth result = Depth(0);

    if(check)
      result += CheckExtension;
    if(singleReply)
      result += SingleReplyExtension;
    if(pos.move_is_pawn_push_to_7th(m))
      result += PawnPushTo7thExtension;
    if(pvNode && recapture)
      result += RecaptureExtension;

    return Min(result, OnePly);
  }

Tord Romstad
Posts: 1808
Joined: Wed Mar 08, 2006 8:19 pm
Location: Oslo, Norway

Re: No mate threat extension in new Glaurung?

Post by Tord Romstad » Mon Jun 11, 2007 2:43 pm

Uri Blass wrote:I wonder if tord found mate threat extension counter productive or he simply did not try it:
It is simply not implemented yet, just like a lot of other search tricks. Glaurung 2 is still in its early infancy. Whether the mate threat extension helps at all is also a question. I don't recall ever having tested it carefully.

A more interesting difference between Glaurung 1 and Glaurung 2 is that the new version extends recaptures at PV nodes. I tried this several times in Glaurung 1, and it always made the strength drop like a stone. In Glaurung 2, it seems to work (although I have not tested enough to be completely sure). I have no idea why.

Tord

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