Accessing optimization iteration in callback function

[jClugstor]

Is there a way that I could get the current iteration of the optimization inside of a callback. I would like to be able to access the number of times the loss function has been called from inside of the callback function.

[Vaibhavdixit02]

It should be available from the iter field of the OptimizationState https://docs.sciml.ai/Optimization/stable/API/optimization_state/#optstate which is the first argument to the callback

[SebastianM-C]

For the number of calls to the loss function, the .original filed would be useful? The number of iterations would be a lower bound on that number.

[Vaibhavdixit02]

Yeah, that's used to populate the fevals field in https://docs.sciml.ai/Optimization/stable/API/optimization_stats/ for some solvers if they return it. We might switch to an Optimization.jl native counter if it makes sense later.

[jClugstor]

Did the first argument to the callback recently change to be an OptimizationState?

[jClugstor]

I see, #649 did it, I think that solves it then, thanks!