Author: Dann Corbit
Date: 11:12:38 03/05/04
Go up one level in this thread
On March 05, 2004 at 09:15:59, Mathieu Pagé wrote:
>On March 05, 2004 at 00:56:20, Tony Werten wrote:
>
>>On March 04, 2004 at 15:16:43, Mathieu Pagé wrote:
>>
>>>Hi,
>>>
>>>I've just change my minimax algorithm for an AB one. (Yes I know i should have
>>>done this long long time ago, but i did want to keep it simple until it could
>>>play a complete game and understand _all_ the chess rules).
>>>
>>>As expected my engines can search deeper (3-4 more plys) than the old version in
>>>the same time, but the NPS drop dramatically, going from 3.6M nodes/s to a
>>>little bit over 2M nodes/s. It's about 44 % decrease.
>>>
>>>I think it is normal that the nps of Minimax was greater then AB's one because
>>>in AB lot of move are generated, but not searched (so they are not add to the
>>>number of nodes)
>>>
>>>but i think that going from 3.6M to 2M is a big difference.
>>
>>Not really. You spend more time in ordering the moves now. Not only the ordering
>>itself, but also a lot more memory references. ie probing the hashtable, probing
>>killertables, maybe history table. And of coarse, you have to remove those moves
>>from the movelist. Did you already split your move generation in captures and
>>non-captures ?
>
>at a first sight your answer seem to confirm what I was expecting, but is your
>answer the same if I tell you that I have (still) no ordering, no hashtable, no
>killertable, no history ...
>
>What I have is a plain AlphaBeta with iterative deepening.
Your iterative deepening needs a hash table. If you don't want to do an
incremental zobrist, just use Ozan Yigit's hash for the whole position:
static unsigned long
sdbm(str)
unsigned char *str;
{
unsigned long hash = 0;
int c;
while (c = *str++)
hash = c + (hash << 6) + (hash << 16) - hash;
return hash;
}
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