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  1. Apache Nemo
  2. NEMO-205

RDD Closure with Broadcast Variables Serialization Bug

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    • Type: Bug
    • Status: Open
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Labels:

      Description

      For example, this does not work.

      val Rc = sc.broadcast(R)
      var msb = sc.broadcast(ms)
      var usb = sc.broadcast(us)

      ms = sc.parallelize(0 until M, slices)
      .map((i : Int) =>update(i, msb.value, usb.value, Rc.value))
      .collect()

      This results in the following exception.

      org.apache.commons.lang.SerializationException: java.io.NotSerializableException: edu.snu.nemo.compiler.frontend.spark.core.SparkContext

      It seems that the 'sc' gets somehow included in the 'map' closure, when using the broadcast variables: Rc/msb/usb.

       

      Interestingly, the following code with the closures declared prior to 'map' works. 

      val Rc = sc.broadcast(R)
      var msb = sc.broadcast(ms)
      var usb = sc.broadcast(us)

      val update_ms = (i : Int) => update(i, msb.value, usb.value, Rc.value)
      val update_us = (i : Int) => update(i, usb.value, msb.value, Rc.value.transpose())

      println(s"Iteration $iter:")
      ms = sc.parallelize(0 until M, slices)
      .map(update_ms)
      .collect()

       

      We should find the root cause and fix the problem, in order to support existing RDD programs that are most likely not written in this way.

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            • Assignee:
              Unassigned
              Reporter:
              johnyangk John Yang
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              Dates

              • Created:
                Updated: