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Subject: Re: negascout and PVS?

Author: Russell Reagan

Date: 02:16:24 07/28/04

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On July 27, 2004 at 06:39:25, Fabien Letouzey wrote:

>I think this difference is Bruce's own interpretation and does not represent the
>original PVS algorithm.  I think that, in the official articles, both PVS and
>NegaScout use what you describe as "negascout" here.
>I might be wrong.
>It seems Bruce's modification is an attempt to integrate the aspiration-search
>assumption with PVS.  This is interesting.

How is "original PVS" different from Bruce's version? I learned Bruce's version
first... :)

int AlphaBeta (int depth, int alpha, int beta)
    BOOL fFoundPv = FALSE;
    if (depth == 0)
        return Evaluate();
    while (MovesLeft()) {
        if (fFoundPv) {
            val = -AlphaBeta(depth - 1, -alpha - 1, -alpha);
            if ((val > alpha) && (val < beta)) // Check for failure.
                val = -AlphaBeta(depth - 1, -beta, -alpha);
        } else
            val = -AlphaBeta(depth - 1, -beta, -alpha);
        if (val >= beta)
            return beta;
        if (val > alpha) {
            alpha = val;
            fFoundPv = TRUE;
    return alpha;

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