Re: Octave on Windows with large arrays ?

[PhilipNienhuis]

Julien Bect-2 wrote
> Le 15/03/2017 à 16:40, PhilipNienhuis a écrit :
>> Julien Bect-2 wrote
>>> Hi all,
>>>
>>> Is there a place where one can find 64 bits binaries for Octave 4.2.x on
>>> Windows with support for large arrays ?
>> How "large" would you want to have them?
>>
>> With the 64-bit binaries onftp.gnu.org/pub/octave/windows  it is easy to
>> create double arrays that are far larger than the 16 GB RAM in my machine
>> and make it start trashing.
> 
> 
> You mean that they already have 64 bits indexing ?

No (AFAIK), but they've been built for 64-bit Windows to take advantage of
the 64-bit architecture. That means that the max *process limit* of 2 or 3
GB for all of Octave + its data is gone. IOW Octave is a real 64-bit
program.
See here for max array sizes:

https://www.gnu.org/software/octave/doc/interpreter/Compiling-Octave-with-64_002dbit-Indexing.html#Compiling-Octave-with-64_002dbit-Indexing

In some places the information there seems a bit contradictionary to me
(again I see 2GB metntioned but that doesn't hold, limits are larger
depending on class of data); the section could use some cleaning up.
E.g., in a 64-bit (not 64-bit indexing!) Octave-4.3.0+ I can do this:

==================================================
>> a = zeros (30000);
>> whos
Variables in the current scope:

   Attr Name        Size                     Bytes  Class
   ==== ====        ====                     =====  =====
        a       30000x30000             7200000000  double
        ans         1x1                          8  double

Total is 900000001 elements using 7200000008 bytes
==================================================

Anyway it isn't hard to cross-build 64-bit indexing Octave with mxe.
Actually all that is needed is to configure mxe-octave with at least
--enable-64 (plus other flags you need).

(JWE made a few changes so that configure flag may have another name now but
"configure --help" will show you the right options.)

Philip




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