Author: Christophe Theron
Date: 00:40:04 10/08/99
Go up one level in this thread
On October 08, 1999 at 00:55:04, Robert Hyatt wrote:
>On October 07, 1999 at 23:58:44, Christophe Theron wrote:
>
>>On October 07, 1999 at 22:55:42, Dave Gomboc wrote:
>>
>>>On October 07, 1999 at 00:58:07, Christophe Theron wrote:
>>>
>>>>On October 06, 1999 at 21:52:28, Nicolas Carrasco wrote:
>>>>
>>>>>Now I am examining how my Alpha Beta cut off's are working!
>>>>>
>>>>>I would be extreamly pleased to know how many nodes your chess engine make at
>>>>>the initial position (if possible without move ordering) at the following
>>>>>depths:
>>>>
>>>>For Chess Tiger 12.0 (with move ordering and selection) the results are:
>>>>
>>>>2- 46
>>>>3- 606
>>>>4- 2088
>>>>5- 3929
>>>>6- 10102
>>>>7- 31441
>>>>
>>>>
>>>> Christophe
>>>
>>>Your odd/even effect is quite a bit larger than I'm used to seeing. Asymmetric
>>>pruning?
>>>
>>>Dave
>>
>>The odd/even effect depends on the position. For example going from level 2 to
>>level 3 takes a lot of work, apparently because the first sequence of capture
>>begins, or maybe checks (?). At that time the move ordering stored from the
>>previous level becomes completely wrong apparently.
>>
>>If you look at the increasing (cumulative) branching factor you get:
>>
>>2 to 3: 14.0x
>>3 to 4: 3.4x
>>4 to 5: 1.9x
>>5 to 6: 2.6x
>>6 to 7: 3.1x
>>
>>So this is not an odd/even effect. Sometimes the odd to even is high, but
>>sometimes the even to odd is higher.
>>
>>As I said, the behaviour is different in each position. Also, at deeper depth it
>>tends to be smaller.
>>
>>
>> Christophe
>
>
>Your numbers looked ok to me. Normally even ply searches are easier than odd
>ply searches due to alpha beta. IE going from 9 to 10 typically only does a
>little more than double the size of the tree, but going from 10 to 11 is a
>big change. Because every move at the root is always looked at. And except
>for the first root move, at the second, fourth, ..., nth ply (n even) you only
>look at one move before exiting with a fail high. For odd depths the last ply
>has to examine all moves, and not just 1 move like in even ply searches.
>
>of course, with extensions, this isn't quite so exact any longer, and it is
>possible that they become 'equal'.
Yes, that's what I notice generally.
Christophe
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