I've tended to use Strings. Params can be created with a validator (isValid) which can ensure users get an immediate error if they try to pass an unsupported String. Not as nice as compile-time errors, but easier on the APIs.
On Mon, Sep 14, 2015 at 6:07 PM, Feynman Liang <fli...@databricks.com> wrote: > We usually write a Java test suite which exercises the public API (e.g. > DCT > <https://github.com/apache/spark/blob/master/mllib/src/test/java/org/apache/spark/ml/feature/JavaDCTSuite.java#L71> > ). > > It may be possible to create a sealed trait with singleton concrete > instances inside of a serializable companion object, the just introduce a > Param[SealedTrait] to the model (e.g. StreamingDecay PR > <https://github.com/apache/spark/pull/8022/files#diff-cea0bec4853b1b2748ec006682218894R99>). > However, this would require Java users to use > CompanionObject$.ConcreteInstanceName to access enum values which isn't the > prettiest syntax. > > Another option would just be to use Strings, which although is not type > safe does simplify implementation. > > On Mon, Sep 14, 2015 at 5:43 PM, Ulanov, Alexander < > alexander.ula...@hpe.com> wrote: > >> Hi Feynman, >> >> >> >> Thank you for suggestion. How can I ensure that there will be no problems >> for Java users? (I only use Scala API) >> >> >> >> Best regards, Alexander >> >> >> >> *From:* Feynman Liang [mailto:fli...@databricks.com] >> *Sent:* Monday, September 14, 2015 5:27 PM >> *To:* Ulanov, Alexander >> *Cc:* dev@spark.apache.org >> *Subject:* Re: Enum parameter in ML >> >> >> >> Since PipelineStages are serializable, the params must also be >> serializable. We also have to keep the Java API in mind. Introducing a new >> enum Param type may work, but we will have to ensure that Java users can >> use it without dealing with ClassTags (I believe Scala will create new >> types for each possible value in the Enum) and that it can be serialized. >> >> >> >> On Mon, Sep 14, 2015 at 4:31 PM, Ulanov, Alexander < >> alexander.ula...@hpe.com> wrote: >> >> Dear Spark developers, >> >> >> >> I am currently implementing the Estimator in ML that has a parameter that >> can take several different values that are mutually exclusive. The most >> appropriate type seems to be Scala Enum ( >> http://www.scala-lang.org/api/current/index.html#scala.Enumeration). >> However, the current ML API has the following parameter types: >> >> BooleanParam, DoubleArrayParam, DoubleParam, FloatParam, IntArrayParam, >> IntParam, LongParam, StringArrayParam >> >> >> >> Should I introduce a new parameter type in ML API that is based on Scala >> Enum? >> >> >> >> Best regards, Alexander >> >> >> > >
