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From MLnick <>
Subject [GitHub] spark pull request #17793: [SPARK-20484][MLLIB] Add documentation to ALS cod...
Date Tue, 02 May 2017 09:50:53 GMT
Github user MLnick commented on a diff in the pull request:
    --- Diff: mllib/src/main/scala/org/apache/spark/ml/recommendation/ALS.scala ---
    @@ -791,32 +813,43 @@ object ALS extends DefaultParamsReadable[ALS] with Logging {
           checkpointInterval: Int = 10,
           seed: Long = 0L)(
           implicit ord: Ordering[ID]): (RDD[(ID, Array[Float])], RDD[(ID, Array[Float])])
= {
         require(!ratings.isEmpty(), s"No ratings available from $ratings")
         require(intermediateRDDStorageLevel != StorageLevel.NONE,
           "ALS is not designed to run without persisting intermediate RDDs.")
         val sc = ratings.sparkContext
    +    // Precompute the rating dependencies of each partition
         val userPart = new ALSPartitioner(numUserBlocks)
         val itemPart = new ALSPartitioner(numItemBlocks)
    -    val userLocalIndexEncoder = new LocalIndexEncoder(userPart.numPartitions)
    -    val itemLocalIndexEncoder = new LocalIndexEncoder(itemPart.numPartitions)
    -    val solver = if (nonnegative) new NNLSSolver else new CholeskySolver
         val blockRatings = partitionRatings(ratings, userPart, itemPart)
         val (userInBlocks, userOutBlocks) =
           makeBlocks("user", blockRatings, userPart, itemPart, intermediateRDDStorageLevel)
    -    // materialize blockRatings and user blocks
    -    userOutBlocks.count()
    +    userOutBlocks.count()    // materialize blockRatings and user blocks
         val swappedBlockRatings = {
           case ((userBlockId, itemBlockId), RatingBlock(userIds, itemIds, localRatings))
             ((itemBlockId, userBlockId), RatingBlock(itemIds, userIds, localRatings))
         val (itemInBlocks, itemOutBlocks) =
           makeBlocks("item", swappedBlockRatings, itemPart, userPart, intermediateRDDStorageLevel)
    -    // materialize item blocks
    -    itemOutBlocks.count()
    +    itemOutBlocks.count()    // materialize item blocks
    +    // Encoders for storing each user/item's partition ID and index within its partition
using a
    --- End diff --
    Why not add the comment before the encoder `val`s are defined? You could add a space in
between the solver if you want to disambiguate the comment

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