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## Re: manipulating sparse matrices

 From: David Bateman Subject: Re: manipulating sparse matrices Date: Sat, 15 Oct 2005 19:27:26 +0200 User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)

```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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```

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Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
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