Diagonal v. sparse matrices

[Jaroslav Hajek]

On Wed, Mar 4, 2009 at 9:47 PM, Jason Riedy <jason at acm.org> wrote:
> And Jaroslav Hajek writes:
>> What's wrong with it? Besides, in current tip you get
>> P =
>> Permutation Matrix
>>    0   1   1
>>    1   0   1
>>    1   1   0
>
> It should be
>    1   0   0
>    0   1   0
>    0   0   1
> to match traditional mathematical notation.
>

Oops, I see. I must be getting blind. That's definitely a bug. I must
have screwed something up.


>> What exactly are you trying to achieve? Remember that most sparse vs.
>> diag ops return a full matrix for compatibility with matlab, and
>> changing that would be a significant breach.
>
> I don't care about Matlab(TM).  I don't use it.  They don't want
> me as a user, personally or as a class; they're targeting a
> different market now.
>
>> That's what I did for the mx-op-defs and MArray-defs. I think there
>> was some speed up, but still not what I was hoping for. So I guess C++
>> is just slow, and we need to live with that.
>
> I'll look into that.  I'd hope it'd break some of the dependency
> chains.  It's the *re*building of everything that's killing me.
>

Do you have a multicore machine? On multiple cores, it's not that bad.
Thank heavens for make -j :)



-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz