## 7-men Syzygy attempt

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Sesse
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### Re: 7-men Syzygy attempt

syzygy wrote:
Sun Jun 03, 2018 10:53 pm
I think the Robin Hood trick should leave the average exactly unchanged. (I am guessing that the double counting of symmetric tables somehow explains the change from 2.06 to 2.05.) Reducing the worst case length is probably a good thing.
FWIW, the supposed advantage is that moving a bunch of elements from 1 to 2 probes is likely to be fairly inconsequential, since the next element is likely to be already in the cache (either on the same cache line, or prefetched), so moving 60 such elements to get one element down from 68 to 8 is an overall win. I haven't measured myself, but it makes sense to me.

I agree the average should have stayed put. I think the reason why it doesn't is a minor bug in my counting, now that I think of it (I don't necessarily look in the overflow bucket).

jwes
Posts: 778
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### Re: 7-men Syzygy attempt

syzygy wrote:
Sun Jun 03, 2018 11:10 pm
According to this page, the average number of probes for successful find is estimated to be

For alpha = 3002/4096, this gives 2.372. So what you measured is better than expected.

For alpha = 3002/8192, we get 1.289, which is slightly better than what you measured.
Have you thought about trying to optimize the hash function for your data? You should be able to find a set of random numbers that give many fewer collisions if you try a few billion.

Sesse
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### Re: 7-men Syzygy attempt

Well, if you want to go down that route, you can use what's known as perfect hashing. But those functions are typically somewhat more expensive to evaluate, so just iterating down a few buckets is probably worth it.

If you try modifying the existing hash values, you mess with a lot more than just the tablebases. That may or may not be harmless.

syzygy
Posts: 4818
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### Re: 7-men Syzygy attempt

jwes wrote:
Mon Jun 04, 2018 1:22 pm
syzygy wrote:
Sun Jun 03, 2018 11:10 pm
According to this page, the average number of probes for successful find is estimated to be

For alpha = 3002/4096, this gives 2.372. So what you measured is better than expected.

For alpha = 3002/8192, we get 1.289, which is slightly better than what you measured.
Have you thought about trying to optimize the hash function for your data? You should be able to find a set of random numbers that give many fewer collisions if you try a few billion.
The current hash function basically comes for free (it is based on the material signature key).

Sesse
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### Re: 7-men Syzygy attempt

Generation passed 5 TB; I guess that's somewhat of a milestone. I assume we're getting more precise estimates of the end size now, too?

Nordlandia
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### Re: 7-men Syzygy attempt

Sesse wrote:
Sun Jun 10, 2018 7:01 am
Generation passed 5 TB; I guess that's somewhat of a milestone. I assume we're getting more precise estimates of the end size now, too?
Maybe compare 5 TB to remaning sets to be generated.

How many sets is finished as of now?

500 out of 1,000 ?

noobpwnftw
Posts: 435
Joined: Sun Nov 08, 2015 10:10 pm

### Re: 7-men Syzygy attempt

Nordlandia wrote:
Sun Jun 10, 2018 10:43 am
500 out of 1,000 ?
337 tables to go, progress of 5v2 pawnful (141/210) & 4v3 pawnful (57/325).

syzygy
Posts: 4818
Joined: Tue Feb 28, 2012 10:56 pm

### Re: 7-men Syzygy attempt

noobpwnftw wrote:
Sun Jun 10, 2018 11:55 am
Nordlandia wrote:
Sun Jun 10, 2018 10:43 am
500 out of 1,000 ?
337 tables to go, progress of 5v2 pawnful (141/210) & 4v3 pawnful (57/325).
I just noticed KRBPPvKQ is missing. Was there any problem with its generation?

Nordlandia
Posts: 2690
Joined: Fri Sep 25, 2015 7:38 pm
Location: Sortland, Norway

### Re: 7-men Syzygy attempt

noobpwnftw wrote:
Sun Jun 10, 2018 11:55 am
Nordlandia wrote:
Sun Jun 10, 2018 10:43 am
500 out of 1,000 ?
337 tables to go, progress of 5v2 pawnful (141/210) & 4v3 pawnful (57/325).
Is it possible to quantify likely file size by sets generated up to this point?

wdl / dtz

noobpwnftw
Posts: 435
Joined: Sun Nov 08, 2015 10:10 pm

### Re: 7-men Syzygy attempt

syzygy wrote:
Sun Jun 10, 2018 12:15 pm
noobpwnftw wrote:
Sun Jun 10, 2018 11:55 am
Nordlandia wrote:
Sun Jun 10, 2018 10:43 am
500 out of 1,000 ?
337 tables to go, progress of 5v2 pawnful (141/210) & 4v3 pawnful (57/325).
I just noticed KRBPPvKQ is missing. Was there any problem with its generation?
KRBBPvKQ is missing somehow, retrying, maybe OOM or a simple mis-hit of Ctrl+C.