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Subject: Re: [OMPI devel] Reviewing MPI_Dims_create
From: Christoph Niethammer (niethammer_at_[hidden])
Date: 2014-02-10 20:39:00

sqrt(2^31)/log(sqrt(2^31))*(1+1.2762/log(sqrt(2^31)))/1024 * 4byte = 18,850133965051 kbyte should do it. ;)
Amazing - I think our systems are still *too small* - lets go for MPI with int64 types. ^^

----- UrsprÃ¼ngliche Mail -----
Von: "Jeff Squyres (jsquyres)" <jsquyres_at_[hidden]>
An: "Open MPI Developers" <devel_at_[hidden]>
Gesendet: Dienstag, 11. Februar 2014 01:32:53
Betreff: Re: [OMPI devel] Reviewing MPI_Dims_create

On Feb 10, 2014, at 7:22 PM, Christoph Niethammer <niethammer_at_[hidden]> wrote:

> 2.) Interesting idea: Using the approximation from the cited paper we should only need around 400 MB to store all primes in the int32 range. Potential for applying compression techniques still present. ^^

Per Andreas' last mail, we only need primes up to sqrt(2B) + 1 more. That *has* to be less than 400MB... right?

sqrt(2B) = 46340. So the upper limit on the size required to hold all the primes from 2...46340 is 46340*sizeof(int) = 185,360 bytes (plus one more, per Andreas, so 185,364).

This is all SWAGing, but I'm assuming the actual number must be *far* less than that...

--
Jeff Squyres
jsquyres_at_[hidden]