[New user]: per iteration hook or callback

[a-jp]

Hi,

Using Pyomo with ipopt.  Would it be possible, every iteration, before any objective or constraint is solved, to call a user defined function?  Is there any example if so?  It's important that I can perform this before any work is done, each iteration, including the first iteration. I would like the function to be passed the current status of model.  

I would equally be interested in a post-completed iteration hook, but the above is explicitly for a pre-iteration hook.

Thanks,

Andy

[a-jp]

It would be good to get confirmation that this can't be done, so I can try to refactor my design?

[Michael Bynum]

There are examples of using callbacks with cyipopt here:

https://github.com/Pyomo/pyomo/tree/main/pyomo/contrib/pynumero/examples/callback

Michael

[a-jp]

thanks, that's really helpful.  Based only on the name and the comments 'intermediate_callback' seems to be for once the work for each iteration as been completed it is called, I need to perform some setup each iteration, and cache complex and expensive functions into an array, is there a callback that can be performed before the iteration begins and before any constraints or objectives are solved for that iteration?

Thanks,

Andy

[a-jp]

Hi Michael,

I wondered if you had any more thoughts about a callback approach/function that I could use at the start of each ipopt iteration rather than at the end?

thanks

Andy