Author: Christophe Theron
Date: 09:34:37 03/30/01
Go up one level in this thread
On March 30, 2001 at 03:29:51, Tony Werten wrote:
>On March 29, 2001 at 22:38:33, Christophe Theron wrote:
>
>>On March 29, 2001 at 16:01:51, Tony Werten wrote:
>>
>>>On March 29, 2001 at 15:12:21, Christophe Theron wrote:
>>>
>>>>On March 29, 2001 at 14:39:34, Tony Werten wrote:
>>>>
>>>>>On March 29, 2001 at 14:21:16, Christophe Theron wrote:
>>>>>
>>>>>>On March 29, 2001 at 13:49:06, Tony Werten wrote:
>>>>>>
>>>>>>>On March 29, 2001 at 13:31:59, Christophe Theron wrote:
>>>>>>>
>>>>>>>>On March 29, 2001 at 09:14:57, Robert Hyatt wrote:
>>>>>>>>
>>>>>>>>>On March 29, 2001 at 06:22:13, Jouni Uski wrote:
>>>>>>>>>
>>>>>>>>>>On March 29, 2001 at 06:17:50, Alexander Kure wrote:
>>>>>>>>>>
>>>>>>>>>>>On March 29, 2001 at 04:37:19, Tony Werten wrote:
>>>>>>>>>>>
>>>>>>>>>>>>Hi all,
>>>>>>>>>>>>
>>>>>>>>>>>>until what depth do various programs probe the tablebases ?
>>>>>>>>>>>>
>>>>>>>>>>>>cheers,
>>>>>>>>>>>>
>>>>>>>>>>>>Tony
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>Hi Tony,
>>>>>>>>>>>
>>>>>>>>>>>In London 2000, I let Nimzo 8 play with a depth of 6 plies, but later I came to
>>>>>>>>>>>the conclusion that 8 plies might be better overall. This is indeed the default
>>>>>>>>>>>setting of NimzoX and Varguz playing on ICC.
>>>>>>>>>>>
>>>>>>>>>>>Greetings
>>>>>>>>>>>Alex
>>>>>>>>>>
>>>>>>>>>>Sorry one stupid question: is this the first or last 6/8 plys?
>>>>>>>>>>
>>>>>>>>>>Jouni
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>His statement would make no sense if it were the _last_ 6-8 plies. Those
>>>>>>>>>are the ones that kill performance if you aren't careful. The first 6-8 plies
>>>>>>>>>don't cost a thing.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>But it could also mean it probes TBs in all the plies except the last 6/8.
>>>>>>>>
>>>>>>>>Meaning that if Nimzo is doing a X plies search, then the program probes the TBs
>>>>>>>>in the tree for all nodes that have a distance from the root below or equal to
>>>>>>>>X-6 (or X-8).
>>>>>>>
>>>>>>>Could be but that would mean, with an average depth of 10 to 12, you'd be
>>>>>>>probing the first 4 to 6 ply. I mean, it helps but it could help more.
>>>>>>>
>>>>>>>That is, not counting extensions, but you if you search 10 ply, you don't know (
>>>>>>>at ply 8 ) how many plies are still coming.
>>>>>>>
>>>>>>>cheers,
>>>>>>>
>>>>>>>Tony
>>>>>>
>>>>>>
>>>>>>But you know how many plies you have done since the root position...
>>>>>
>>>>>2 possibilities:
>>>>>- We are talking about different things
>>>>>- I don't get it
>>>>>
>>>>>Might be both.
>>>>>
>>>>>Tony
>>>>
>>>>
>>>>You don't know how many extensions you are going to do, so you just ignore
>>>>extensions and assume you are going to search full width the same number of
>>>>plies as your iteration number.
>>>>
>>>>So at iteration 10, stop probing TBs after two moves from the root (assuming
>>>>like Nimzo that you don't probe in the last 8 plies of search).
>>>>
>>>>That is why I say "you know how many plies you have done since the root
>>>>position...".
>>>
>>>But then you don't have almost no depths where you probe. (In your example only
>>>ply 1 and 2 )
>>
>>
>>
>>Yes, but your NPS does not go too low then.
>>
>>It's a compromise between speed of search and accuracy of the evaluation.
>>
>>Don't forget that accessing a TB slot can be as expensive as searching 1000
>>nodes (depends on your program). And that many TB accesses are just a waste of
>>time because they are not going to have any influence on your main line.
>>
>>I'm not saying that 8 plies like in Nimzo is the right number (actually I'm not
>>even sure that Nimzo does it this way).
>>
>>In Tiger I stop accessing the tablebases a few plies before I reach the horizon.
>>If I don't do that the program gets much weaker because of the dramatically
>>slower NPS.
>
>Make your program slower !
>
>XiniX is a slow searcher and I'm testing on slow hardware so I hardly notice a
>slowdown because of probing. ( Might not be the best solution )
>
>The idea I have for probing a lot is that if a position is worth being searched,
>it's probably worth being probed. ( Unless you're very near to the leafs )
>
>Hmm, search position normal, then store no nodes in hashtable, then when
>searched second time: if n.o. nodes>1000 do probe. I'll have a try.
>Maybe combined with: first x ply always probe.
>
>Positions below current position stored in hashtable can help with enhanced
>transposition cutoffs as well.
>
>I'll put it in my totry book.
>
>Tony
If you search 1000 positions per second and your hard disk is fast enough to
make 1000 probes per second, don't hesitate, you can probe everywhere in the
tree.
But if you can make 100000 NPS, then probing always will weaken your program
significantly.
That's also why you need 2 days to implement TBs in a program, and 2 months to
have them working right (improving the strength of your program).
Christophe
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