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Subject: Re: EGTB generation with 1 bit per position?

Author: martin fierz

Date: 01:35:42 03/26/03

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On March 25, 2003 at 17:58:33, Eugene Nalimov wrote:

>On March 25, 2003 at 17:30:52, martin fierz wrote:
>
>>i computed some checkers endgame databases with retrograde analysis based on the
>>paper by the chinook team. for larger databases, i have a memory size problem;
>>specially as win32 only allows a process to use 2GB.
>>i once heard that it was possible to compute a win/loss/draw endgame database
>>using only 1 bit per position as opposed to 2 bits as i was using up to now (and
>>like in the chinook paper).
>>
>>does someone here know more about this? i'm looking either for an explanation
>>for dummies, or for a reference to a paper.
>>
>>thanks in advance
>>  martin
>
>Actually, you can force Windows NT/2k/XP to give your application 3Gb, not 2Gb.
>Search for /3Gb switch at Microsoft web site. Application should be "clean",
>i.e. it should not assume that high pointer bit is always zero. For such
>applications you should  specify linker flag /LARGEADDRESSAWARE.

i know - but 2 or 3GB; it doesn't really matter. it's just a limitation that
makes more memory-efficient algorithms necessary.

>One more note: you probably will not be able to allocate 3Gb in one chunk, but
>you'll be able to allocate 30 100Mb chunks.
>
>Of course you can use Win64 where you don't need those tricks :-)

i'd like to but i don't have the $$$$ necessary for that. a win32 machine with
2GB ram is MUCH cheaper than a win64 machine with 2GB ram :-(

>And now returning to the original question: with easily "reversable" index
>function you need *random* access not to two bitmaps, but only to one. This way
>you can generate first bitmap in memory, flush it to disk, generate second
>bitmap, and then sequently walk through first bitmap using small (several
>megabytes) buffer.

umm, i asked for an explanation for dummies. this one is beyond me :-)
do you have a reference to a paper where this is explained in more detail?

cheers
  martin



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