integrate_ode_rk45 - expose step_size?

[Sebastian Weber]

Hi!

I was just going through the integrate_ode_rk45 and found that the initial step_size gets exposed as an option. I thought we only expose abs+rel tol and max_num_steps, but not step_size, no?

The step_size gets automatically adjusted by the rk45 algorithm according to abs+rel tolerance specifications. To me it would make sense to export step_size if we were to expose rk4 which uses a fixed step size all the time, but the initial step size should not matter performance wise for the rk45 (ok, up to an epsilon).

Maybe I was wrong in my understanding of what we decided.

Best,
Sebastian

[Michael Betancourt]

It would make sense to maintain non-adaptive settings such as
relative and absolute tolerances and max steps as the only arguments.

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[Daniel Lee]

Ok.

[Bob Carpenter]

Daniel --- can you remove the initial step size? I haven't
had time to work on this yet, and now worry I won't have time
until later next week.

- Bob

[Daniel Lee]

Yes. I'll have it on the branch shortly.