Author: Robert Hyatt
Date: 21:16:24 02/12/01
Go up one level in this thread
On February 12, 2001 at 23:00:36, William Bryant wrote:
>On February 12, 2001 at 22:39:21, William Bryant wrote:
>
>>My understand is, Internal Iterataive Deepening is used when searching the
>>root PV node and you encounter a position for which there is no hash table
>>best move. Specifically, this is done during the full width part of the
>>tree (rather than the PVS part of the search).
>>
>>My program at present tests for this by comparing beta to alpha.
>>ie if (beta == alpha+1) then this is the PVS part of the tree and IID should
>>be skipped.
>>
>>This doesn't help at all so I think I'm missing something in the implementation.
>>
>>Any comments or suggestions would be appreciated.
>>
>>William
>>wbryant@ix.netcom.com
>
>For Clarity,
>
>if ((there_is_no_best_move) && (beta != alpha + 1)) {
> //do internal iterative deepening
> }
>
>William
That is almost what I do...
if (tree->hash_move[ply]==0 && do_null && depth>=3*INCPLY) do {
if (ply & 1) {
if (alpha!=root_alpha || beta!=root_beta) break;
}
else {
if (alpha!=-root_beta || beta!=-root_alpha) break;
}
Which says (a) no hash move; (b) null-move is legal here (which means the
move at the previous ply was _not_ a null-move; (c) 3 plies of depth left
to search (or more); (d) alpha and beta are _exactly_ as they were at the
start of the iteration.
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