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Subject: Re: Sparse matrix indexing speed -- shape sensitivity
Date: Mon, 29 Aug 2011 10:30:07 -0400
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"Matt J " <mattjacREMOVE@THISieee.spam> wrote in message 
news:j3efp3$h5h$1@newscl01ah.mathworks.com...
> "Bruno Luong" <b.luong@fogale.findmycountry> wrote in message 
> <j3dtcs$rjq$1@newscl01ah.mathworks.com>...
>>
>> 2) As I understand they way ndSparse combine the n-1 index to 1 linear 
>> index is a limitation. Are you able to store an ndSparse of dimension 
>> [1e6 1e6 1e6 10] (even an empty one)?
> =================
>
> No, it's true, I cannot. But of course, MATLAB already has limitations 
> similar to this presently on its 2D sparse matrices which user's must work 
> around. Why should it be that this all-zero matrix stores perfectly fine
>
> A=sparse(1e8,1);
>
> but not its transpose,
>
>>> A.';
> ??? Error using ==> transpose
> Out of memory. Type HELP MEMORY for your options.
>
>
> Anyway, if extending the indexing supported by setsparse/getsparse is not 
> easy to do, it's not worth the effort.


In the User Guide discussing sparse, there is this statement:

For more information on how MATLAB stores sparse matrices, see John R. 
Gilbert, Cleve Moler , and Robert Schreiber's Sparse Matrices In Matlab: 
Design and Implementation, (SIAM Journal on Matrix Analysis and Applications 
, 13:1, 333356 (1992)).  (link: 
http://www.mathworks.com/help/pdf_doc/otherdocs/simax.pdf)

-- 
Loren
http://blogs.mathworks.com/loren/
http://www.mathworks.com/matlabcentral/