[Beowulf] large array to run

Robert G. Brown rgb at phy.duke.edu
Thu Dec 13 17:56:43 EST 2007


On Thu, 13 Dec 2007, Geoff Jacobs wrote:

> Mark Hahn wrote:
>>> When I try to use the array of
>>> integer actual(9915,9915,9915)
>>
>> I don't speak fortran natively, but isn't that array
>> approximately 3.6 TB in size?
>
> Oops, forgot to put the decimal in the right place.
>
> 9915^3 * 8 bits/integer / 1024^3 bytes/GB = 907 GB.
>
> It could be done with a 64 bit kernel. Too big for PAE.

Yeah, if you had a box with several hundred memory slots....

Which I say only semi-sarcastically.  They sound like they're coming,
they're coming.  Who knows, maybe they're here and I'm just out of
touch.

If it is a sparse matrix, them just maybe one can do something on this
scale, but otherwise, well, it's like telling mathematica to go and
compute umpty-something factorial -- it will go out, make a herioc
effort, use all the free memory in the universe, and die valiantly
(perhaps taking down your computer with it if the kernel happens to need
some memory at a critical time when their isn't any).  Large scale
computation as a DOS attack...

    rgb

>
>

-- 
Robert G. Brown
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone(cell): 1-919-280-8443
Web: http://www.phy.duke.edu/~rgb
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