Github user vrilleup commented on the pull request:
https://github.com/apache/spark/pull/964#issuecomment-47964502
@yangliuyu did you persist the underlying RDD[Vector] behind RowMatrix?
This RDD is used in every iteration, caching will improve run time a lot. From
my tests, if the RDD is persist(), the first call to aggregate takes 10s to
1min, while any subsequent aggregate takes less than 1s.
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