No mate threat extension in new Glaurung?

[Uri Blass]

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]

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