Re: problem with the octave built-in function "kron"

[Stephen Montgomery-Smith]

On 05/03/2013 11:33 AM, c. wrote:
> 
> On 3 May 2013, at 18:28, Stephen Montgomery-Smith <address@hidden> wrote:
> 
>> Use speye instead of eye.
> Unlike Matlab, in Octave eye uses less memory than speye:
> 
> ----------------------------------------------------------------
>>> a = eye (7);
>>> b = speye (7);
>>> whos a b
> Variables in the current scope:
> 
>    Attr Name        Size                     Bytes  Class
>    ==== ====        ====                     =====  =====
>         a           7x7                         56  double
>         b           7x7                        116  double
> 
> Total is 56 elements using 172 bytes
> ----------------------------------------------------------------
> 
> that's because Octave has a special class for diagonal matrices wich allows 
> to only store the 
> diagonal elements:
> 
> ----------------------------------------------------------------
>>> typeinfo (a)
> ans = diagonal matrix
>>> typeinfo (b)
> ans = sparse matrix
>>>

However kron seems to treat diagonal matrices and sparse matrices
differently.  Maybe kron should be rewritten to see if both of the
matrices are sparse OR diagonal.  Because when I took his code and
changed eye to speye, it worked.

I should add that I tested it using a very old version of octave that
comes with ubuntu linux.  Maybe this fix has already been applied in
later versions.