Author: Christophe Theron
Date: 11:42:34 03/30/01
Go up one level in this thread
On March 30, 2001 at 13:00:35, Robert Hyatt wrote:
>On March 30, 2001 at 12:28:20, Christophe Theron wrote:
>
>>On March 30, 2001 at 09:30:06, Vincent Diepeveen 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).
>>>>
>>>>I don't think that probing the TBs in the first 6/8 plies of the search makes
>>>>any sense.
>>>
>>>Do yo mean this in absolute terms or do you mean this in
>>>terms of "doing probes last few plies like qsearch is more important
>>>as doing probes in the first 8 plies?"
>>>
>>>In the first case i would disagree. in the second case i would agree.
>>
>>
>>What I wanted to say is that probing the TBs in the first 6/8 plies ONLY does
>>not make sense.
>>
>>I mean that there must be some mechanism to somehow relate the depth of the
>>probing to the depth of the search.
>>
>>If you are going to depth 25 at this time, you certainly don't want to stop
>>probing the TBs at depth 8.
>>
>>However Alex answered something that is still unclear to me which would suggest
>>that in the first 8 plies he does some kind of probe, and he does another kind
>>of probe in the next plies. But I can be wrong here.
>>
>>
>> Christophe
>
>
>That is what they do. They load the win/lose/draw tables into memory, but
>they don't have them _all_ in that format. They probe the normal tables
>early in the search where the cost is low. They probe the w/l/d tables
>everywhere else as there is no I/O required. This means that for the w/l/d
>tables, you only get a bound on the value and you could get into a never-ending
>mate in N loop. But by probing the real tables early in the tree, they will get
>the right distance-to-mate scores where it really matters...
>
>This has been discussed before. The only problem I pointed out is that if you
>do all the 3-4-5 piece tables as win/lose/draw, you _still_ need over a gigabyte
>of memory to hold the result. That is still too big, and now that we are 40
>gigabytes into the 6 piece files, forget win/lose/draw for them.
OK I see now.
Well it's a smart trick and I guess that storing in memory the WDL TBs for 4-men
positions only would already be an improvement...
However I wonder how many elo points they get with these WDL TBs... It's quite a
programming effort to implement them I guess.
On the other hand, if you use the memory required to store the WDL TB for other
purposes, like extending your hash tables, maybe you get the same kind of ELO
increase?
So I wonder if it's really worth it.
Christophe
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