Re: indexing improvements - advice wanted

[David Bateman]

Jaroslav Hajek wrote:
> On Mon, Oct 27, 2008 at 7:36 PM, Jaroslav Hajek <address@hidden> wrote:
>   
> > > Also it seems to me that a
> > > case like
> > >
> > > A = speye(1e6,1e6)
> > > A (A != 0) = randn(1e6,1);
> > >
> > >       
> > Currently, I've only dealt with dense array indexing. I haven't yet
> > looked at sparse arrays, so I'm not even sure I can achieve some
> > optimizations there. In the current patch the only minor changes to
> > the sparse code are those caused by the changed idx_vector interface.
> > But I definitely intend to look at sparse matrices as well, at minimum
> > I want to clean up the interfaces as I did with Array<T>.
> >     

Ok, I looked at your patch and it seems that you haven't yet taken into 
account the sparse indexing and assign at all as the methods "freeze" 
and "clear_index" of the index class are still used, and you've removed 
these from the idx_vector class. So something will have to be changes there.

In any case it wasn't the indexing of sparse variables that I was 
mentioning here, but rather the use of a sparse variable as an index... 
A real sparse variable doesn't make much sense as an index, as the zeros 
in the variable will result in indexing errors, so conversion of this to 
a full array before using it as an index is a reasonable thing to do (to 
treat the case where a full matrix is stored as a sparse matrix). 
However when the sparse matrix is logical it in fact makes a lot of 
sense like in the example I gave above. The fact that the above will 
explode my memory at the moment has always annoyed me.

> The updated patch is uploaded, this time passing the test suite.
> There were no flawed tests, after all - they were all bugs in my code.
> So, the only changes in tests are caused by the different error
> messages.
> Of course, the presented speed-up numbers do still hold.
>
> Unless anyone objects, I'd like to apply this after 3.2.x is forked.
>   
Seems fine to me..

D.

--
David Bateman                                address@hidden
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