[Help-gsl] ode-initval

[mc_pork]

Dear GSL users,

I would be very happy and thankful if one of you could help me out on the 
following issue:

I am using the GSL package for ODE integration of a PDE which I turn into a 
large set of ODEs using the Method of Lines.

I am however unsure about the setting of the values for abserr and relerr. Is 
it correct that the initially provided h value gets adapted to meet the needs 
demanded by abserr and relerr?

And how does that work? Whatever of the two abserr and relerr is satisfied 
first? Because in the example program provided with the documentation, relerr 
is set to zero.

Another question is about how to do a convergence test? For that I would need 
three different ODE evaluations using different stepsizes h. How would I 
proceed with the GSL routines here, since they use adaptive stepsizes? Should I 
use three different choices for abserr and relerr instead?

Thank you very much for your time and help!

Toni
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