Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: Rebel's long checks concept in QS

Author: milix

Date: 09:38:07 01/24/04

Go up one level in this thread


Ok, I tried the ideas posted here but no success.
My new code goes like this:

quiescent(alpha, beta, mate_score, checks_depth)
{
   score = full_evaluate()
   if (score >= beta) return score // or beta, same effect
   if (score > alpha) alpha = score

   if (side_to_move_is_in_check)
      generate_legal_moves()
      if (no_legal_moves) return -mate_score
      else if (only_one_legal_move) checks_depth = checks_depth + 3
      else if (only_two_legal_moves) checks_depth = checks_depth + 2
   else if (checks_depth > 0)
      generate_good_equal_captures_queenpromotions_and_checks()
   else generate_good_equal_captures_queenpromotions()
   sort_the_moves()

   if (checks_depth < 0) checks_depth = 0
   if (checks_depth > 3) checks_depth = 3

   for each move in the list {
      make_the_move()
      score = -quiescent(-beta, -alpha, mate_score-1, checks_depth-1)
      undo_the_move()
      if (score >= beta) return score // or beta, same effect
      if (score > alpha) alpha = score;
   }

   return alpha
}

Tried to
   if (checks_depth <= 0 and score >= beta) return score
but QS exploded.

Tried Ed's suggestion to call QS with alpha=LOWVALUE (=MATE_SCORE-SOME_MARGINE)
but failed also.

My main search is a PVS Alpha-Beta and for this test i search only in depth 1. I
use no extensions, no TT (only a repetion-check wich works ok). My move-list
sorting algorithm is a SEE which puts checks on the top (for this test).
I call my main search from root search as

alpha_beta(1, -INFINITY, +INFINITY, MATE_SCORE)

For the test position

FEN "2k4r/ppp5/2p1b1Q1/4q3/3bP3/3B2P1/PPP1N2P/5R1K b - - 0 1"

I got (briefly):

.......
 After QS Score for Bd4xb2 is -1.05
Trying move Rxh2
GOING TO QS WITH Rxh2: SIDE TO MOVE IS IN CHECK
-----------------------------------------------
 QS called with args (-3000000, 1046, 299999, 3)
 Generated moves for White: Kxh2
  QS move played Kh1xh2
  QS called with args (-1046, -1034, 299998, 2)
  Generated moves for Black: Qh8 Bg1 Bxa2 Qxg3 Qh5
   QS move played Qe5-h8
   QS called with args (1034, 1046, 299997, 1)
   Generated moves for White: Qh5 Qh7 Qh6 Kg2
    QS move played Qg6-h5
    QS called with args (-1046, -6263, 299996, 0)
    score=6263
   score=-1046
   QS move played Bd4-g1
......
and missed the mate.

When I icreased checks_depth by 4 (or 3 points) it again missed the mate.

Finally, it suggests Bd4xb2 in all cases....



This page took 0.02 seconds to execute

Last modified: Thu, 07 Jul 11 08:48:38 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.