Author: Robert Hyatt
Date: 10:00:35 03/30/01
Go up one level in this thread
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.
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