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From "Matthias Boehm (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SYSTEMML-1543) Parfor remote result merge fails w/ stackoverflowerror from rdd union
Date Wed, 19 Apr 2017 01:16:41 GMT
Matthias Boehm created SYSTEMML-1543:
----------------------------------------

             Summary: Parfor remote result merge fails w/ stackoverflowerror from rdd union
                 Key: SYSTEMML-1543
                 URL: https://issues.apache.org/jira/browse/SYSTEMML-1543
             Project: SystemML
          Issue Type: Bug
            Reporter: Matthias Boehm
            Priority: Blocker


The current parfor remote_spark result merge is implemented as (1) a union over all output
files from individual parfor tasks, and (2) a final aggregation with or without compare. For
many parfor tasks, the union of such many RDDs leads to stack overflow errors as shown below:
{code}
Exception in thread "main" java.lang.StackOverflowError
        at org.apache.spark.rdd.UnionRDD$$anonfun$1.apply(UnionRDD.scala:84)
        at org.apache.spark.rdd.UnionRDD$$anonfun$1.apply(UnionRDD.scala:84)
        at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
        at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
        at scala.collection.immutable.List.foreach(List.scala:381)
        at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
        at scala.collection.immutable.List.map(List.scala:285)
        at org.apache.spark.rdd.UnionRDD.getPartitions(UnionRDD.scala:84)
        at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:252)
        at org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:250)
        at scala.Option.getOrElse(Option.scala:121)
        at org.apache.spark.rdd.RDD.partitions(RDD.scala:250)
        at org.apache.spark.rdd.UnionRDD$$anonfun$1.apply(UnionRDD.scala:84)
        at org.apache.spark.rdd.UnionRDD$$anonfun$1.apply(UnionRDD.scala:84)
        at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
        at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
        at scala.collection.immutable.List.foreach(List.scala:381)
{code}

This is not show up before because the parfor optimizer usually compiles in-memory result
merge operations if the outputs are moderately small, i.e., they fit into the driver.



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