Re: elements of a sparse matrix

[Jaroslav Hajek]

2010/12/27 Jaana Tommiska <address@hidden>:
> Jordi Gutiérrez Hermoso kirjoitti 27.12.2010 kello 18:10:
>>
>> What's the density of your matrix? What was the exact call to sprand?
>> I'm noticing that the density matters a lot.
>
>
>>
>> Yes, but I'm curious why wouldn't it work otherwise. Can you provide a
>> reproducible test case?
>>
> I wrote these lines
> B=sprand(20000,10000,0.01);
> A=B'*B;
> A(10000,10000)
> or
> A(10000*10000)
>
> I am interested if the matrix A is too big to fit in the memory?
> thanks
> Jaana
>
>

If you get over the A = B'*B line, the matrix size is definitely not
too big. In this case, both expressions should work equally (in
general, they may not, however), and they indeed do work equally for
me. If it doesn't work for you, you've found a bug. Whether that is
interesting, depends on your version of Octave.