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Subject: Re: 7-man endgames - questions

Author: Vincent Diepeveen

Date: 12:36:08 08/29/05

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On August 29, 2005 at 14:41:00, Marc Bourzutschky wrote:

>On August 29, 2005 at 13:46:48, Vincent Diepeveen wrote:
>
>>On August 29, 2005 at 13:13:33, Marc Bourzutschky wrote:
>>
>>>On August 29, 2005 at 10:27:17, Vincent Diepeveen wrote:
>>>
>>>>On August 29, 2005 at 03:15:54, Marc Bourzutschky wrote:
>>>>
>>>>Hi Marc,
>>>>
>>>>I just don't understand how you manage to generate a mate in 250 with
>>>>just 500GB i/o size for krbn krb.
>>>>
>>>>I need like 2 TB raid5 array or something for my generator for 7 men
>>>>I'm using bitmaps which are similar to mate in n, though not entirely,
>>>>as i just care for WDL.
>>>>
>>>>that means you basically need from -mate256 to +mate255 = 9 bits per
>>>>entry.
>>>>
>>>>Diep's entry size is probably bigger with 358G entries than what is possible
>>>>if you use nalimov's scheme, i'm using my own one which simply avoids more than
>>>>1 piece at the same square, no illegal reductions are getting done.
>>>>
>>>>Anyway. 2 files of 358G * 9 bits per entry is more like 800GB than it is
>>>>close to 500GB.
>>>>
>>>>How do you fit this EGTB onto just 500GB disk?
>>>>
>>>
>>>As described in the post, we split krbnkrb into two components, depending on the
>>>relative color of the bishops.  This reduces the problem to two independent
>>>generations with each half the size.  In addition, we use on-the-fly
>>>compression.  We used less than 250 GB during generation.
>>
>>Hello Marc,
>>
>>Thanks for your answer!
>>
>>So you didn't split the bishops in 4 components:
>>  white bishop for KRBN side and white bishop for KRB
>>  white bishop for KRBN side and black bishop for KRB
>>  black bishop for KRBN side and white bishop for KRB
>>  black bishop for KRBN side and black bishop for KRB
>>
>>of course assuming you rotate 8 fold over the king positions and
>>not the bishop (as there is less bishops in that case).
>>
>
>No, since we restrict ourselves to the usual 462 symmetry equivalent king
>positions for pawnless endings.  The color of any individual bishop cannot be
>fixed, because some of the symmetry operations to get the kings into one of
>those 462 positions would change the color of the bishop.  Only the relative
>color of two bishops can be fixed, since that is invariant to all the symmetry
>operations.

Ah yes, i had forgotten this, how dumb of me!

>>how many entries does your indexing scheme use for one of those
>>files KRBNKRB?
>
>462*(64^5)/2

In diep format it's 462 * 62 * 61 * 60 * 59 * 58 = 358752350880
Versus your format is half of 462 * 64^5         = 496068722688

Without pawns it's easy to calculate it by hand. With pawns it's
very hard to calculate it by hand as i must look it up in the table
first because a king on a1 gives other pawnreduction than king on b2 :)

So if i understand well, uncompressed the 4 files are nearly 1T entries,
when you would use 1 byte per entry. Probably you had no other option than
that from speed viewpoint as otherwise you can't see so many positions per
second on average. I calculated your generator gets like 30 million
positions per second, when also counting the lazy evaluated ones. This is
very impressive!

Note in the last generator i build (i built 3 generators over the time)
it is using also a different format than the diep WDL egtb's is using,
because working with 64 possibilities goes a hell of a lot faster, for the
same reason. It's basically cpu speed that is needed. A small disk array
of 8 harddisks and a 4ware raid card already gives at raid0 like 400MB per
second which would support speeds of up to several hundreds of millions of
positions per second.

I assume you used raid0 for both harddisks?

If not your generator speed might be quite some faster when adding some array
speeds. Because a single IDE can get a throughput of at most like 50MB/s,
which at 1 byte per entry would be 50 million positions.

Note in diep generator format i use 1 bit per position at generation time.

>>how many bytes (or bits) per entry did you use at generation time?
>
>Only a few bitmaps for a subset of the 462 king-king positions are in memory
>during generation.  1 bitmap for 19 different king-king positions, plus two
>additional bitmaps for a given king position.  A general 7-man endgame thus
>requires 21 * 64^5 / 8 = 2.8 GB of RAM.  With permutation symmetries or bishop
>parity tricks this can be reduced accordingly.
>
>We'll give more details in a technical paper we are working on.

No need, really, your posts are really appreciated on this matter.

Keep doing the good work!

Oh, i hardly dare to ask as someone who has everything privateware himself,
but is your resulting EGTB downloadable somewhere?

Vincent

>-Marc



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