Fix passing of superstep in Bagel to avoid seeing new values of the

superstep value upon recomputation, and set the default storage level in
Bagel to MEMORY_AND_DISK

bagel/src/main/scala/spark/bagel/Bagel.scala

@@ -7,8 +7,7 @@ import scala.collection.mutable.ArrayBuffer
 import storage.StorageLevel
 
 object Bagel extends Logging {
-
-  val DEFAULT_STORAGE_LEVEL  = StorageLevel.MEMORY_ONLY
+  val DEFAULT_STORAGE_LEVEL = StorageLevel.MEMORY_AND_DISK
 
   /**
    * Runs a Bagel program.
@@ -63,8 +62,9 @@ object Bagel extends Logging {
       val combinedMsgs = msgs.combineByKey(
         combiner.createCombiner _, combiner.mergeMsg _, combiner.mergeCombiners _, partitioner)
       val grouped = combinedMsgs.groupWith(verts)
+      val superstep_ = superstep  // Create a read-only copy of superstep for capture in closure
       val (processed, numMsgs, numActiveVerts) =
-        comp[K, V, M, C](sc, grouped, compute(_, _, aggregated, superstep), storageLevel)
+        comp[K, V, M, C](sc, grouped, compute(_, _, aggregated, superstep_), storageLevel)
 
       val timeTaken = System.currentTimeMillis - startTime
       logInfo("Superstep %d took %d s".format(superstep, timeTaken / 1000))