[SciPy-user] openopt vs. cvxopt, 'f' vs. 'd','z'

dmitrey dmitrey.kroshko@scipy....
Wed Jan 30 13:40:06 CST 2008


Mclean Edwards wrote:
> The numbers turn out to be the same, as I had previously made an error on 
> my end.  (I needed r.xf[-1] for my optimal value instead of r.ff, due 
> to a problem transformation.)
> The speed for openopt-cvxopt and cvxopt are 
> also comparable (~15% overhead for a couple of runs on small problems).
>   
As for speed, there is the following issue: cvxopt LP & QP solvers 
require a parameter True/False to treat problem sparse or dense. I 
decided not to overwhelm OO users additional parameters, moreover, 
lpSolve and glpk has no the one, they determine it by themselves, 
according to sparsity of matrices. So I decided to call "sparse" CVXOPT 
solvers if numberNonZeros/FullSize<0.3, and "dense" otherwise. So the 
time elapsed and results can be a little bit different (because other 
algs were used).
> Dmitrey, you deserve some praise.  Openopt is a good package, and I am 
> very glad you are developing it.  
Thank you, however, it would be much more better, would anyone mention 
something like that in my guestbook - it could help me to achieve a 
finance support via grant.
Regards, D.
> When I'm finally able to get some 
> preliminary code done myself, I would be glad to contribute.
>
> I'm off to play around some more with the NLP solvers.
>
> Cheers,
>
> Mclean
>   



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