Workflow Components
Optimization workflow building blocks.
The building blocks live in submodules: compute_steps, event_handlers,
evaluators, executors, and concurrency.
They fit together in one direction. A compute step drives a run and emits events about it; event handlers receive those events; an evaluator produces the function values the step asks for; and an executor is where an evaluator sends the work, if it sends it anywhere. Each is given to the next explicitly, so a workflow is whatever the caller wires up: nothing here looks around for the parts it needs.
None of these objects can be used across a process boundary. They may be pickled as part of a payload, but arrive in a worker as inert placeholders, which the worker reports rather than silently using.