Re: What limits the largest size of matrix?

[David Bateman]

Michael Creel wrote:
> Thanks to everyone who responded. OK, that make sense. I'm a bit
> surprised that 2.9.12 lets this go by without comment. How can that
> be? I checked octave_config_info on both versions, and I see 
> USE_64_BIT_IDX_T = false, which I guess confirms my quite clear memory
> that I didn't use the --enable-64 option. At one point in the past I
> tried to use --enable-64, but got poor results. If this is expected to
> work well with 2.9.14, I'd be happy to try it again.
> Michael
>

The change that affects this is

2007-05-31  John W. Eaton  <address@hidden>

        * Array.cc (Array::get_size): Throw std::bad_alloc exception if
        the computed size is too large for the size of Octave's index type.


And the comment in the code about this is

// The following get_size functions will throw a std::bad_alloc ()
// exception if the requested size is larger than can be indexed by
// octave_idx_type.  This may be smaller than the actual amount of
// memory that can be safely allocated on a system.  However, if we
// don't fail here, we can end up with a mysterious crash inside a
// function that is iterating over an array using octave_idx_type
// indices.

So yes this was fixed after 2.9.12. As for the --enable-64 option it
should be getting better, but all the external dependencies of Octave
need to be compiled for 64 bit as well, and in particular with Atlas
that is only supported in the latest 3.7 releases. Therefore, I still
consider it a bit of a pain to build..

Regards
David

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