[Help-gsl] Jacobian evaluation in ODE suite

[Claude Lacoursiere]

Hello.

I'm using the ODE module in a class I teach and I was surprised that the
Jacobian function is unused for all integration methods with the exception of
gsl_odeiv_step_bsimp

I tried all methods on the BZ reaction which is very stiff, and none of

gsl_odeiv_step_rk2imp
gsl_odeiv_step_rk4imp
gsl_odeiv_step_gear2

used the provided Jacobian function a single time.

Using either the Matlab toolbox or the Octave odepkg, all implicit methods need
to evaluate the Jacobian to produce a decent solution for this
equation.  True, neither
of these have the Gauss'  colocation method available in GSL.

Does anyone know how to force the evaluation of Jacobians?  Is this a bug?

Attached is the code if anyone is curious.

Best,
/Claude

bz.c
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