[SciPy-dev] Implementing a distance matrix between two sets of vectors concept

[David Cournapeau]

Peter Skomoroch wrote:
> You're right, I was thinking the sparse data structures would help 
> with storing the input vectors themselves during the computation 
> rather than the final matrix (which will need to be 1/2 M*N if the 
> distance is symmetric)...this comes up a lot in collaborative 
> filtering where the dimensionality of the vectors is high, but most of 
> the vector entries are missing.
Ok, that this basically means supporting sparse input, right ? I have to 
say that I don't know anything about sparse implementations issues in 
numpy (or any other language for that matter). I guess that performances 
mainly depend on the flexibility between matrix representation and data 
storage. Are sparse arrays directly supported in numpy ?

David