Re: [ojAlgo-user] v25.1

[Oddvar G. <od...@pr...>]

>> Do you have any hints/links that can put me on the right track to  
>> pre-solve the system myself?

>Don't feel I know the best way to fix your problem.

>The AE matrix contains some very small elements like for instance  
>-3.4914813388431334E-15. This is a constraint parameter?! Having  
>parameters with very different magnitude could be a problem, but in  
>this case the number itself is just too small.

Ok, I see. Just so you don't think I take the numbers out of the air :-): That small number is the result of a cosine call with an angle close to pi/2. The angle is actually a direction of a moving object, and can take the value of any number between - pi and pi. Such numbers are also common in control systems (i.e. Model Predictive Control) due to rounding errors. 
I'll try to remove such numbers before calling the QP solver.

>> Or do you have any plans for developing a pre-solver?

>Yes...

Great! 

Thanks again.

- Oddvar

>/Anders


> Thanks for your help!
>
> - Oddvar
>
> -----Original Message-----
>> From: Anders Peterson [mailto:an...@op...]
> Sent: 23. november 2008 21:10
> To: Anders Peterson
> Subject: Re: [ojAlgo-user] v25.1
>
> On 21 nov 2008, at 12.40, Anders Peterson wrote:
>
>> On 21 nov 2008, at 10.07, Oddvar Grønning wrote:
>>
>>> I have a dynamic optimization problem to solve that mostly is
>>> overdetermined, so the optimization problem has a set of solutions
>>> instead of one global solution. I guess this is the reason of the
>>> numerical difficulties of my systems.
>>
>> Yes, I think the problem is that you have several (near) redundant
>> constraints.
>
> Don't think so anymore...
>
> I've long felt that the QP solvers needed a pre-solver that analysed
> and fixed the model/problem for better numerical performance. I think
> that the Matlab solver has one, and that's the difference. By
> experimenting a bit I managed to improve the quality of the solution
> to your latest model/problem:
>
> {{0.0},
> {0.0175},
> {-0.0175},
> {1.4639},
> {5.0},
> {4.8768},
> {4.4581},
> {-6.7724},
> {0.2257}}
>
> This solution is VERY close to the what you got from Matlab!
>
> Until ojAlgo actually has such a pre-solver you have to think about
> how you construct your matrices.
>
> /Anders
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