Re: manipulating sparse matrices

[David Bateman]

Mike Miller a écrit :

> On Sat, 15 Oct 2005, David Bateman wrote:
>
> > nzmax is in 2.9, as the source-forge index was I believe based on a 
> > 2.9.2 release, it should probably be updated soon as many things have 
> > changed (eg statistics functions, etc). The 0bytes is a missing 
> > feature in the octave-forge sparse functions as the bytes size in the 
> > whos function I believe was added at 2.1.58, after the octave-forge 
> > sparse stuff was written. Basically, it needs to implement a 
> > byte_size() function to return the value that will be printed.. This 
> > also works in 2.9.3
>
>
> For the meantime, stuck as I am in the 2.1.71 world (because I'm 
> developing code for users who can install 2.1.71), can I estimate 
> nzmax by taking 8*nnz()?  It seems that full matrices use 8 bytes per 
> element.  Or maybe it should be 3*8*nnz() because every sparse element 
> requires three terms: row, column and value.

Not quite. Its more like

(ncol + 1) * sizeof(octave_idx_type) + nz * (sizeof(octave_idx_type) + 
sizeof(double))

for a real matrix, and you can imagine what it is for Complex and bool 
matrices. octave_idx_type is either int or long and so is 4 bytes on a 
32 bit platform and can be either 4 or 8 bytes on a 64 bit platform [at 
least with 2.9 :-) ]


> > As you were asking about cholesky factorizations previously, I've 
> > just gotten sparse cholesky factorizations working with cholmod and 
> > will commit this soon, I want to try to address the chol2inv, cholinv 
> > and inv functions, and update the docs first though...
>
>
> Excellent!
>
> You guys are great.  Thanks.
>
> I suppose that Octave 2.9.x will be released someday as Octave 3.0. Is 
> that the plan?
That more or least John's plan, though there are still lots of things on 
the timeline before then...

D.


> Mike
>
>
>
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