From:	mert0407 AT sable DOT ox DOT ac DOT uk (George Foot)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: need help handling enormous size arrays
Date:	Wed, 05 Feb 1997 21:59:00 GMT
Organization:	Oxford University
Lines:	28
Message-ID:	<32f90055.22691415@news.ox.ac.uk>
References:	<5d916e$c1e AT hecate DOT umd DOT edu>
NNTP-Posting-Host:	mc31.merton.ox.ac.uk
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

On 5 Feb 1997 04:09:50 GMT, jasonp AT Glue DOT umd DOT edu (Jason Stratos
Papadopoulos) wrote:

>Hello. I'm writing a homebrew arbitrary precision arithmetic package,
>and was coding up a multiply that uses fast Fourier transforms. Everything
>is nice and fast up to array (of doubles) size 2^14, but from 2^15 on
>the computation time hits a brick wall! Before this point (2^10,11,12,etc)
>a given power of 2 only takes a bit more than twice as long as the one
>before. The program does no memory management, and I need to work with
>array sizes perhaps as large as 2^18 or 2^19. 
>
>Am I not doing somethng vital? My hard drive isn't thrashing so it's
>not a virtual memory problem; For the record, I have 16 megs of ram
>and about 20 or 30 megs of free HD space; I'm using a Win95 DOS box
>for dpmi.
>
>Please don't flame me for missing the obvious...I'm an amateur at
>high-powered scientific computing.
>
>Thanks in advance,
>jasonp

If it's not too long, please post your source code - enough to work
and demonstrate the problem, but not more than is necessary. If you
are missing something, it won't be obvious to anyone if you don't give
it to us :)

George Foot

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