tensorflow / tensorflow/probability

Missing preference for parameters in tfp.math.psd_kernels.RationalQuadratic

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Description

There are two exclusive parameters in tfp.math.psd_kernels.RationalQuadratic. The first is length_scale, and the second is inverse_length_scale. But both are marked as preferred -- it is the default value in the ParameterProperties.
If the length_scale is less stable, it should be changed to:

...
length_scale=parameter_properties.ParameterProperties(
            is_preferred=False,
            default_constraining_bijector_fn=(
                lambda: softplus.Softplus(low=dtype_util.eps(dtype)))),
...

https://github.com/tensorflow/probability/blob/0759c57eb0306a5bb0fcc3d105bbcab9943092a5/tensorflow_probability/python/math/psd_kernels/rational_quadratic.py#L214

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Research direction

Start with tensorflow_probability/python/math/psd_kernels/rational_quadratic.py around line 214 and inspect the ParameterProperties for the two exclusive parameters. Confirm which parameter should be preferred, update the metadata accordingly, and verify the RationalQuadratic tests covering parameter selection and constraining bijectors.

Written by the indexing model from the issue text.

Assessment

Tech stack
python, tensorflow
Domain
machine-learning
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
48/100

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