[MBDyn-users] Naive solver fails with ill conditioned jacobian matrices

Paolo Mantegazza mantegazza at aero.polimi.it
Wed Apr 4 14:29:50 CEST 2012


Resch Reinhard wrote:
> Dear Mr. Masarati,
> 
>  
> 
> Recently I had troubles with the Naive linear solver if the condition 
> number of the jacobian matrix was too high. I have tried to scale my 
> equations in order to improve the condition number but I was not able to 
> reach the convergence with the Naive solver. All other solvers (Umfpack, 
> KLU, Y12, and Lapack) worked fine.
> 
>  
> 
> The condition number of my jacobian matrix was approximately 1e10.
> 
>  
> 
> Do you know if the Naive solver is sensitive to ill conditioned matrices?
> 

It should not be different from any other solver. Likely its default 
parameters, e.g. pivoting threshold and depth, are chosen by 
compromising  between efficiency and stability in a way that is 
unsuitable for your problem. Try playing with its parameters.

paolo Mantegazza

>  
> 
> Best regards,
> 
>  
> 
> Reinhard Resch
> 
> 
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