RE: Octave 3.0

[Schloegl Alois]

Zitat von Andy Adler <address@hidden>:

> On Wed, 26 Feb 2003, Schloegl Alois wrote:
> >  * Sparse matrices:
> > An important issue is the matrix multiplication of full and sparse
> matrices.
> > See the following example:
> >
> > x = [-inf, -1, 0, 1, inf,nan];
> > sx= sparse(x);
> > full(x'*x)
> > full(sx'*sx)
> >
> > The point is that under some circumstances (0*inf, 0*-inf, 0*nan), matrix
> > multiplications of full and sparse matrices give different results.
> > SPARSE can be used to control the desired behavior. Therefore, SPARSE is
> > important and, currently, there is no workaround. IMHO, SPARSE has top
> > priority.
> 
> Have you looked at the sparse matrix functions in octave-forge?
> Are there any specific features lacking in that package?
> 
> Andy


Andy, 

I was referring to John's priority list. IMO, it is a good thing, if sparse 
arrays become part of core octave.

Unfortunately, I've only access to some outdated versions of Octave (2.1.40), 
without a recent version of octave-forge. Hence, I can not say whether I miss a 
specific feature in your sparse package. Only, the following example should 
return the result below:


x = [-inf, -1, 0, 1, inf,nan];
sx= sparse(x);
full(x'*x)
full(sx'*sx)



ans =

   Inf   Inf   NaN  -Inf  -Inf   NaN
   Inf     1     0    -1  -Inf   NaN
   NaN     0     0     0   NaN   NaN
  -Inf    -1     0     1   Inf   NaN
  -Inf  -Inf   NaN   Inf   Inf   NaN
   NaN   NaN   NaN   NaN   NaN   NaN


ans =

   Inf   Inf     0  -Inf  -Inf   NaN
   Inf     1     0    -1  -Inf   NaN
     0     0     0     0     0     0
  -Inf    -1     0     1   Inf   NaN
  -Inf  -Inf     0   Inf   Inf   NaN
   NaN   NaN     0   NaN   NaN   NaN

Alois 



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