Re: [Help-gsl] odeiv2 rk2imp driver time step

[Farkas, Illes]

Hello,

This is the ODE system:

f[0] = 2 - 3 * y[0]
f[1] =      2 * y[0] - y[1] - 2 * y[0] * y[1]

Replacing rk2imp with bsimp has solved the problem.

Thanks
Illes


2011/12/21 Tuomo Keskitalo <address@hidden>

> Hello,
>
>
> On 12/22/2011 12:07 AM, Farkas, Illes wrote:
>
>  5s ) later there is an update when gsl_odeiv2_driver_apply returns the
>> FAILURE value: -1. After logging the current time directly from the
>> "function" and "jacobian" (used by the gsl_odeiv2_system, which is
>> driver by the driver), I found that this particular update fails,
>> because the time step is halved again and again until it reaches the
>> limit of numerical precision.
>>
>
> Sounds like you're driving into a singularity.
>
> Try different steppers (msbdf, bsimp). If they're all stopping about
> there, the problem might be with your system. I guess you either have a bug
> in rhs function or jacobian code, or your system really has a singluarity
> in it. Or maybe you just have inappropriate tolerances in relation to your
> system?
>
> BR,
> Tuomo
>
> --
> address@hidden
> http://iki.fi/tuomo.keskitalo
>



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