New features

[sixpearls]

I made a few changes to the CVODE interface that I needed for a project that I wanted share with the main distribution in case it was of interest. Since I was merely prototyping I have several features/changes that committed on top of each other:

• make options dict and and with_userdata flag public (done for prototyping, not attached to this one)
• the ability to pass userdata to the jacfn (I did not actually end up using this for my project, but it seemed like someone else had it almost working)
• allow max_step_size to be changed after the solver has been instantiated (used in my project)
• allow arbitrary values of tstop option to be used rather than enforcing strictly positive (used in my project)
• adding a wrapper to the CVodeGetRootInfo method which "returns an array showing which functions were found to have a root" according to the SUNDIALS docs (used in my project)

Are any/all of these changes of interest? If so, would a monolithic PR be acceptable or do they need to be split into individual PRs? Once the features are approved, I can update the docs and add tests as appropriate.

Best,
Ben

[sixpearls]

Hi @aragilar, it seems like you are the current maintainer of this package. When you have the chance could you provide input on this PR? Thanks,

[aragilar]

I think if you split them up it would make it easier to review. At a quick glance:

• CVodeGetRootInfo seems like something useful to add
• I'm not sure if the changes to tstop and max_step_size are safe, it would be good to confirm that both changes don't break some underlying assumption (otherwise I have no objection).
• I'm not sure why jacfn didn't include the userdata passing, there may have been a reason for that (though maybe it was that there was an alternative way of passing in data)?
• I'm wary of making both options and with_userdata public, as they are internal state which should be set via the various functions and helpers.