Author: Tim
Date: 14:51:45 01/28/00
I know what principal variation search is.
But I don't understand returned value when window size so small.
This is principal variation search algorithm.
if (Firstmove) {
value=-Search(-beta,-alpha);
Firstmove=0;
}
else {
value=-Search(-alpha-1,-alpha);
if ((value > alpha) && (value < beta))
value=-Search(-beta,-alpha);
}
Above code says:
If it is not the first move, search with window size 1.
if value <= alpha or value >= beta, we don't have to search again.
if value > alpha and value < beta, search again with normal window size.
But how can we sure value is always correct when value <= alpha or value >=
beta?
And how can we sure value is always incorrect when value > alpha and value <
beta?
Thank you in advance.
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