Author: Robert Hyatt
Date: 07:18:45 02/13/01
Go up one level in this thread
On February 13, 2001 at 03:03:16, Tim Foden wrote:
>On February 13, 2001 at 00:16:24, Robert Hyatt wrote:
>
>>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.
>
>I think I understand the reasons for (a), (c) and (d) above. I'm note sure
>about (b) -- why do we want to make sure that the previous ply was not a null
>move?
>
>Cheers, Tim.
I don't want to waste the time just to do a null-move search. IE IID is not
cheap and after a null-move, normal ordering usually works pretty well. It is
worth testing to be sure, of course...
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