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A few general questions...
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H.G.Muller



Joined: 10 Mar 2006
Posts: 12767
Location: Amsterdam
PostPost subject: Re: A few general questions...    Posted: Tue Jan 31, 2012 8:18 pm Reply to topic Reply with quote
Zach Wegner wrote:
And incorrect, because it does not handle aspiration fail lows.


Well, I'd rather call it incomplete than incorrect. We were discussing the fail highs here. I already mentioned above that you would have to re-search all moves if in the end you have a fail low. If you insist to see that in the pseudo code:

Code:
RootSearch()
{
  GenerateMoves();
  firstMove = TRUE;
  for(depth = 1; depth < maxDepth; ) {
    SetAspirationWindow();
    bestMove = NULL;
    for(ALL_MOVES) {
      MakeMove();
      score = -Search((firstMove ? -alpha-1 : -beta), -alpha);
      if(score > alpha) {
        if(!firstMove && score < beta) score = -Search(-beta, -alpha); // PVS
        if(score >= beta) { // aspiration fail high
          score = -Search(-INF, -alpha);
        }
      }
      UnMake();
      if(score > alpha) {
        alpha = score;
        bestMove = move;
        if(score>beta) beta = score+1;
      }
      firstMove = FALSE;
      TakeNodeStats(move);
    }
    if(bestMove == NULL) { alpha = -INF; continue; }
    SortMoves();
    depth = NextDepth(depth);
  }
}


But this whole discussion is going off at a tangent, which leaves my original question still unsanswered. So let me try again:

Do all we agree that a re-search on a move that with window {alpha, beta} gave a score < beta, in general will not produce a different score, when the sre-search uses a window {alpha, beta'}, beta' > beta? (If you are lucky by an immediate hash hit in the daughter node?)

And that when you know in advance that the result of a score will be a fail low, it would be pointless to do that search?

Only if you do not agree with one of these two points would it make sense to contradict me. Otherwise, it would suffice to say: "indeed, it is pointless, but everyone does it like that, so I would not dare to do it differently"... Laughing

Another interesting thought: if everyone does it like this, while it makes no sense, it can only be because they are copying each other's implementation...
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Display posts from previous:   
Subject Author Date/Time
A few general questions... Bill Henry Sun Jan 29, 2012 8:09 pm
      Re: A few general questions... Robert Purves Sun Jan 29, 2012 9:11 pm
      Re: A few general questions... Evert Glebbeek Sun Jan 29, 2012 9:16 pm
      Re: A few general questions... Don Dailey Mon Jan 30, 2012 1:44 pm
            Re: A few general questions... Bill Henry Mon Jan 30, 2012 2:12 pm
                  Re: A few general questions... H.G.Muller Mon Jan 30, 2012 2:24 pm
                  Re: A few general questions... Don Dailey Mon Jan 30, 2012 2:42 pm
                        Re: A few general questions... Bill Henry Mon Jan 30, 2012 3:59 pm
                              Re: A few general questions... Don Dailey Mon Jan 30, 2012 4:12 pm
                                    Re: A few general questions... Bill Henry Mon Jan 30, 2012 4:54 pm
                        Re: A few general questions... Robert Purves Mon Jan 30, 2012 9:25 pm
                        Re: A few general questions... Sven Schüle Tue Jan 31, 2012 12:02 am
                              Re: A few general questions... H.G.Muller Tue Jan 31, 2012 8:53 am
                                    Re: A few general questions... Sven Schüle Tue Jan 31, 2012 12:08 pm
                                          Re: A few general questions... H.G.Muller Tue Jan 31, 2012 12:14 pm
                                                Re: A few general questions... Sven Schüle Tue Jan 31, 2012 12:53 pm
                                                      Re: A few general questions... H.G.Muller Tue Jan 31, 2012 1:56 pm
                                                            Re: A few general questions... Don Dailey Tue Jan 31, 2012 2:24 pm
                                                                  Re: A few general questions... H.G.Muller Tue Jan 31, 2012 4:26 pm
                                                                        Re: A few general questions... Michel Van den Bergh Tue Jan 31, 2012 4:33 pm
                                                                              Re: A few general questions... H.G.Muller Tue Jan 31, 2012 5:39 pm
                                                                        Re: A few general questions... Don Dailey Tue Jan 31, 2012 5:03 pm
                                                            Re: A few general questions... Sven Schüle Tue Jan 31, 2012 3:35 pm
                                                                  Re: A few general questions... Evert Glebbeek Tue Jan 31, 2012 4:24 pm
                                                                  Re: A few general questions... H.G.Muller Tue Jan 31, 2012 5:25 pm
                                                                        Re: A few general questions... Zach Wegner Tue Jan 31, 2012 7:13 pm
                                                                              Re: A few general questions... H.G.Muller Tue Jan 31, 2012 8:18 pm
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