Author: Tord Romstad
Date: 12:40:46 10/02/03
Go up one level in this thread
On October 02, 2003 at 14:45:53, Uri Blass wrote:
>On October 02, 2003 at 13:56:07, Tord Romstad wrote:
>
>>On October 02, 2003 at 13:34:15, Anthony Cozzie wrote:
>>
>>>If I understand it correctly, implementing the BM extension in Zappa would go
>>>like so (pseudoish):
>>>
>>> do_null_search();
>>> rb->null_threat = rb->best_move;
>>> if(ply >= 2 && m_f_loc((rb-2)->null_threat) == m_f_loc(rb->null_threat))
>>> trigger_extension();
>>
>>Yes, something like that, assuming that rb->best_move contains the move
>>that refuted the null move, and that the function m_f_loc() returns the
>>'target' of the move.
>>
>>This is a simplified version of my code:
>>
>> if(ok_to_do_null_move()) {
>> make_null_move();
>> null_value = -search(-gamma+1, depth-(R+1)*PLY);
>> unmake_null_move();
>> if(null_value >= gamma) return null_value;
>>
>> /* Botvinnik-Markoff extension */
>> if(null_value < margin) {
>> ThreatMove[Ply] = CurrentMove[Ply+1];
>> if((To(ThreatMove[Ply])==To(CurrentMove[Ply-2]) &&
>> To(ThreatMove[Ply-2])==From(CurrentMove[Ply-2])) ||
>> (To(ThreatMove[Ply]) != To(CurrentMove[Ply-2]) &&
>> To(ThreatMove[Ply]) == To(ThreatMove[Ply-2])))
>> bm_ext = 1; /* Trigger Botvinnik-Markoff extension */ }
>> else ThreatMove[Ply] = 0; }}
>>
>>Tord
>
>1)Do you do special steps to remember currentmove[ply+1]?
No.
>I remember the last move that I made at depth ply+1 but if the qsearch after
>null generates no moves then I may remember wrong move from previous search.
>
>I can see 2 solutions to this problem (one to remember the nodes after null move
>and another solution is to remember last move as null move in case that qsearch
>makes no nodes).
When the null move is refuted by standing pat in qsearch, CurrentMove[Ply+1]
will be 0.
>2)Do you check if you threat the same square also in case when the square is
>empty so it can be mate threat in the same square?
Yes. This is why my program solves WAC141 one ply earlier with the
Botvinnik-Markoff extension enabled.
Tord
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