https://issues.apache.org/jira/browse/SPARK-139
https://issues.apache.org/jira/browse/SPARK-1476
https://issues.apache.org/jira/browse/SPARK-6235
You'll hit this bug when your model size is larger than 2GB.
BTW, Recomputation of RDDs may result in duplicated accumulator updates. So please do not use accumulator in your trainer for gradient summation. They know that, but they said they will not fix that.