Currently, the Scala implementation of OneVsRest allows the user to run a parallel implementation in which each class is evaluated in a different thread. This implementation allows up to a 2X speedup as determined by experiments but is not currently not tunable. Furthermore, the python implementation of OneVsRest does not parallelize at all. It would be useful to add a parallel, tunable implementation of OneVsRest to the python library in order to speed up the algorithm.
A ticket for the Scala implementation of this classifier is here: https://issues.apache.org/jira/browse/SPARK-21028