Github user danielyli commented on a diff in the pull request:
https://github.com/apache/spark/pull/17793#discussion_r113894646
--- 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)
.persist(intermediateRDDStorageLevel)
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 = blockRatings.map {
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 --
I moved the code because otherwise the comment on L823 (`// Precompute the
rating dependencies of each partition`) would reference the
`LocalIndexEncoder`s and the `solver`. Agreed that otherwise it would be
unnecessary to move.
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