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Re: Octave Limits


From: Daryl Warkentin
Subject: Re: Octave Limits
Date: Mon, 24 Nov 2003 10:42:54 -0600

On Mon, 2003-11-24 at 09:54, Przemek Klosowski wrote:
>    Upon further inspection I have found that Octave does seem to have a
>    file size limit of 2GB. 
>                     ....
>    I got the following error while running one of my scripts:
> 
>    File size limit exceeded
> 
>    And the file was exactly 2GB. This happens on both ext3 and FAT32 
>    filesystems. I am running a 2.4.21 kernel.
> 
> Ah, but that is a separate issue: currently, octave internally can only
> handle a 2GB single object, because it uses int pointers. That is why
> I said that there should be no limit if octave makes individual, small reads
> and writes to a file---what you are doing is probably reading into 
> a single array. 

Nope. I store approximately 500MB in memory at a time.

octave:1> testfile = fopen('/home/warkentin/Stuff/testdata', 'w+', 'native');
octave:2> testdata = ones(50000000, 1);
octave:3> while(1)
> fwrite(testfile, testdata, 'char', 0, 'native');
> end
panic: File size limit exceeded -- stopping myself...
attempting to save variables to `octave-core'...

address@hidden Stuff]$ ls -l testdata
-rw-rw-r--    1 warkentin warkentin 2147483647 Nov 24 10:39 testdata


> BTW, you will be in a world of pain if you are trying to manipulate
> 2GB+ memory objects on a 32-bit architecture such as x86. Octave may
> need a fix, but you do need to run octave on a platform such as MIPS,
> SPARC, Itanium, or AMD x86-64. Since MIPS, SPARC, Itanium are either
> outrageously expensive, or low performance, or both, AMD Opteron class
> 64-bit CPUs are basically your only choice.

Stuck with an AMD 2800+ and 1.5GB RAM. Would love an Opteron.

> DISCLAIMER: this is my personal opinion, not known to, or reflecting
> the position of, my employer; contents may settle; void where
> prohibited, etc.
> 
> 
>           p
-- 
Daryl Warkentin, P. Eng.
Hardware Engineering
SED Systems
www.sedsystems.ca



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