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https://issues.apache.org/jira/browse/SPARK-20486?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hyukjin Kwon updated SPARK-20486:
---------------------------------
Labels: bulk-closed (was: )
> Encapsulate ALS in-block and out-block data structures and methods into a
> separate class
> ----------------------------------------------------------------------------------------
>
> Key: SPARK-20486
> URL: https://issues.apache.org/jira/browse/SPARK-20486
> Project: Spark
> Issue Type: Improvement
> Components: ML, MLlib
> Affects Versions: 2.1.0
> Reporter: Daniel Li
> Priority: Trivial
> Labels: bulk-closed
>
> The in-block and out-block data structures in the ALS code is currently
> calculated within the {{ALS.train}} method itself. I propose to move this
> code, along with its helper functions, into a separate class to encapsulate
> the creation of the blocks. This has the added benefit of allowing us to
> include a comprehensive Scaladoc to this new class to explain in detail how
> this core part of the algorithm works.
> Proposal:
> {code}
> private[recommendation] final case class RatingBlocks[ID](
> userIn: RDD[(Int, InBlock[ID])],
> userOut: RDD[(Int, OutBlock)],
> itemIn: RDD[(Int, InBlock[ID])],
> itemOut: RDD[(Int, OutBlock)]
> )
> private[recommendation] object RatingBlocks {
> def create[ID: ClassTag: Ordering](
> ratings: RDD[Rating[ID]],
> numUserBlocks: Int,
> numItemBlocks: Int,
> storageLevel: StorageLevel = StorageLevel.MEMORY_AND_DISK):
> RatingBlocks[ID] = {
> val userPart = new ALSPartitioner(numUserBlocks)
> val itemPart = new ALSPartitioner(numItemBlocks)
> val blockRatings =
> partitionRatings(ratings, userPart, itemPart)
> .persist(storageLevel)
> val (userInBlocks, userOutBlocks) =
> makeBlocks("user", blockRatings, userPart, itemPart, storageLevel)
> 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,
> storageLevel)
> itemOutBlocks.count() // materialize item blocks
> blockRatings.unpersist()
> new RatingBlocks(userInBlocks, userOutBlocks, itemInBlocks, itemOutBlocks)
> }
> private[this] def partitionRatings[ID: ClassTag](...) = {
> // existing code goes here verbatim
> }
> private[this] def makeBlocks[ID: ClassTag](...) = {
> // existing code goes here verbatim
> }
> }
> {code}
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