Re: Finding Stable Points in a system of ODEs
07 May '12 08:43
The COPASI error message indicates that COPASI is trying its last
attempt in finding a steady-state by backwards integration in time. This
very often fails with the error message you see.
Since Newton and forward integration did not find a steady-state please
have a look at your time course to get an idea of whether your system
actually has a steady-state. If on of your variables keeps increasing
your system does not have a steady-state and thus COPASI will not be
able to find it. You may also reduce resolution in steady-state task
which defaults to 1e-9 to e.g. 1e-6.
I could help you with details of your model if you send it to me.
On 5/7/12 10:34 AM, ayesha wrote:
> Thank you Herbert, Luca and Stephan for your suggestions.
> I have already tried COPASI, but it could not solve the system (it think it is too stiff).
>> EXCEPTION 2012-05-07 09:39:27<
> CTrajectoryMethod (6): Deterministic integration failed. LSODA reported:
> DLSODA- At T(=R1) and step size H(=R2), the error
> test failed repeatedly or with ABS(H) = HMIN
> In above message, R1 = '85.1645', R2 = '1.61925e-09'
> Please see result for indications of numerical instability.
>> EXCEPTION 2012-05-07 09:39:28<
> CTrajectoryMethod (25): Invalid state at time '-0.010000'.
>> WARNING 2012-05-07 09:39:29<
> CEigen (2): Failed to compute Eigen value with index '70'.
>> WARNING 2012-05-07 09:39:30<
> CEigen (2): Failed to compute Eigen value with index '69'.
> I don't know how far I should go in integration. I have set the current iteration limit to be very high though (1e+06).
> Therefore, just knowing if the system has any stable point or not would be useful.
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Stefan Hoops, Ph.D.
Senior Project Associate
Virginia Bioinformatics Institute - 0477
Bioinformatics Facility II
Blacksburg, Va 24061, USA
Phone: (540) 231-1799
Fax: (540) 231-2606
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