Author: Omid David
Date: 06:19:43 06/01/02
Go up one level in this thread
On June 01, 2002 at 09:13:53, José Carlos wrote:
>On May 31, 2002 at 18:50:18, Omid David wrote:
>
>>I forgot to change "negascout" to "AlphaBeta" in 7th line for better
>>illustration. Here is the correction:
>
>1: int AspWin(int estimate, int delta, int depth)
>2: {
>3: int alpha = estimate - delta;
>4: int beta = estimate + delta;
>5: int best;
>6:
>7: best = AlphaBeta(alpha, beta, depth);
>8:
>9: /* re-search */
>10: if(best <= alpha)
>11: best = AlphaBeta(-10000, beta, depth);
>12: else if(best >= beta)
>13: best = AlphaBeta(alpha, 10000, depth);
>14:
>15: /* is there any better way to handle this very rare case? */
>16: if(best >= beta || best <= alpha)
>17: best = AlphaBeta(-10000, 10000, depth);
>18:
>19: return best;
>20: }
>
> I numbered the lines for clarity. I think it should be:
>
>11: {alpha = -10000; best = AlphaBeta(-10000, beta, depth);}
>13: {beta = 10000; best = AlphaBeta(alpha, 10000, depth);}
>
> If you don't update alpha and beta when researching, it can happen that you
>fail low for [alpha,beta], then you research with [-inf,beta] and return best
>with -inf < best < alpha which is a true score and there's no need to research.
>Same for fail high.
> Other than this, you're code looks correct.
>
> José C.
But then in line 13 it would be in fact AlphaBeta(-10000, 10000, depth) since
alpha = -10000 in line 11. My question is how can a full window search of
(-10000,10000) be avoided at all costs?
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