Re: performance problem with unique on sparse arrays

[David Bateman]

Jaroslav Hajek wrote:
> Hi David,
>
> I started modernizing the Sparse indexing interface. In particular the
> interfaces are updated so that idx_vector is passed by a const
> reference and bool flags are used rather than int. I removed the
> obsolete calls like idx_vector::freeze and improved the code using new
> features from octave_sort and idx_vector, and in the end I ended with
> a rewrite, along with some induced changes.
>
>
>   
<snip>
> so it doesn't seem I slowed something down significantly except
> perhaps the sparse row vector.
> In that case, the scalar and cont. range is specialized, otherwise the
> array is converted to full, indexed, and then sparsified.
> I thought this was OK because a sparse row vector takes O(nc) space
> anyway, so it's an inefficient way to store a sparse vector. Sparse
> column vector is the way to go here.
>
> You're welcome to review the changes and comment on them.
>   
I took a look at this code and it seems find to me. I suspect the row 
vector code was probably already pretty good so you could get much of an 
improvement and the cases where you are slower are just in the noise. It 
seems my previous patch didn't last long ;-)

> I'll address the 2D indexing next, then eventually indexed assignment.
>   
That's going to be a bit harder, and the assign stuff even harder 
again.. But hey one step at a time..

Cheers
David



> regards
>
>   


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