Changing a Range Parameter To Fixed

At some point during my experiment, some of my integer parameters that were originally Range params converge to a single value. At that point, instead of trimming the range to two values, I create a new search space, replace those parameters in the search space with a single FixedParameter, then set the search space on the experiment. However, i then begin receiving this error:

https://github.com/facebook/Ax/blob/1febe3342896805bc9204c414a1d473cee15f485/ax/modelbridge/transforms/remove_fixed.py#L46

I’m curious why this happens. Here is an example:

My parameter, “source” converged to 3 and was replaced by a FixedParameter.

The params in the function are:

obsf.parameters: {'source': 2} 
self.fixed_parameters: { 'source': FixedParameter(name='source', parameter_type=INT, value=3)}

The error is:

Fixed parameter source with out of design value: 2 passed to RemoveFixed.

My only guess is that it is still generating values for the Fixed parameters because they used to be RangeParams, and the old experiment is being loaded from the database as a RangeParam.

[2timesjay]

@belotelov, @tonyhammainen

the solution using “fixed_features” in gen (see https://github.com/facebook/Ax/issues/383#issuecomment-692210541 ) should work once a recently landed fix in master is released. This should also give the desired behavior in terms of fitting the model to the full data but only generating points in the selected slice.

The fix is here: https://github.com/facebook/Ax/commit/f1d77592be5bb0fe42a5182299074e479bdcf780 It prevents overly aggressive filtering when new constraints are added mid-optimization.

An alternative before that release: run a trial manually with an arm that matches your fixed_features, then proceeding with the fixed_features kwarg in gen.

We generally don’t have good support for editing the types of parameters in a search space directly.

[lena-kashtelyan]

@XRen615, yep the stable version is delayed a bit this time due to some pretty exciting updates we plan to publish with it : ) It should be coming towards the end of June.