Are ML .Net models deterministic?

[rebecca-burwei]

Some models are inherently stochastic, others are deterministic. Are ML .Net models deterministic? In other words, given the same input, will an ML .Net model always return the same output/prediction? If so, to how many decimal places is this prediction deterministic?

[frank-dong-ms-zz]

@rebecca-burwei Yes, I believe ML.NET models are deterministic if you use them properly, we have bunch of tests verifying various of model outputs. Regarding the decimal places I believe it is related to the input data and model settings like how many rounds of training will be performed, floating point error will accumulate with the calculation.
@justinormont cc Justin see if Justin has more insights on this questions.

[justinormont]

Model prediction

If you have a trained model, it is almost always deterministic. One example where it's not is if it includes the CountTargetEncoder. See: #4514 (review)

Model training

Some parts of ML․NET can be deterministic. In general practice I wouldn't assume model training is fully deterministic.

Setting a seed in the MLContext and disabling multi-threading gets you close.

Many components also have their own seed values to set. There's a bit of a usability bug in ML․NET as non-hashing seeds should fall-back to the global seed, but the code wasn't added to do so in all components. See: #4752 (comment)

If you're using the AutoML APIs, there's a bit of a butterfly effect in model sweeping due to the small model differences being amplified. See: #4986 (comment)

[frank-dong-ms-zz]

Close this issue as answer has already been provided, @rebecca-burwei feel free to reopen if you have any follow up questions, thanks.