Joseph K. Bradley created SPARK-6682:
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Summary: Deprecate static train and use builder instead for
Scala/Java
Key: SPARK-6682
URL: https://issues.apache.org/jira/browse/SPARK-6682
Project: Spark
Issue Type: Improvement
Components: MLlib
Affects Versions: 1.3.0
Reporter: Joseph K. Bradley
In MLlib, we have for some time been unofficially moving away from the old
static train() methods and moving towards builder patterns. This JIRA is to
discuss this move and (hopefully) make it official.
"Old static train()" API:
{code}
val myModel = NaiveBayes.train(myData, ...)
{code}
"New builder pattern" API:
{code}
val nb = new NaiveBayes().setLambda(0.1)
val myModel = nb.train(myData)
{code}
Pros of the builder pattern:
* Much less code when algorithms have many parameters. Since Java does not
support default arguments, we required *many* duplicated static train() methods
(for each prefix set of arguments).
* Helps to enforce default parameters. Users should ideally not have to even
think about setting parameters if they just want to try an algorithm quickly.
* Matches spark.ml API
Cons:
* In Python APIs, static train methods are more "Pythonic."
Proposal:
* Scala/Java: We should start deprecating the old static train() methods. We
must keep them for API stability, but deprecating will help with API
consistency, making it clear that everyone should use the builder pattern. As
we deprecate them, we should make sure that the builder pattern supports all
parameters.
* Python: Keep static train methods.
CC: [~mengxr]
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