Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/7360#discussion_r34605895
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/fpm/LocalPrefixSpan.scala ---
@@ -76,38 +79,25 @@ private[fpm] object LocalPrefixSpan extends Logging
with Serializable {
}
}
+ def project(database: Iterable[Array[Int]], prefix: Int):
Iterable[Array[Int]] = {
+ database
+ .map(candidateSeq => getSuffix(prefix, candidateSeq))
+ .filter(_.nonEmpty)
+ }
+
/**
* Generates frequent items by filtering the input data using minimal
count level.
- * @param minCount the absolute minimum count
- * @param sequences sequences data
- * @return array of item and count pair
+ * @param minCount the minimum count for an item to be frequent
+ * @param database database of sequences
+ * @return item and count pairs
*/
private def getFreqItemAndCounts(
minCount: Long,
- sequences: Array[Array[Int]]): Array[(Int, Long)] = {
- sequences.flatMap(_.distinct)
- .groupBy(x => x)
- .mapValues(_.length.toLong)
+ database: Iterable[Array[Int]]): Iterable[(Int, Long)] = {
+ database.flatMap(_.distinct)
+ .foldRight(Map[Int, Long]().withDefaultValue(0L)) { case (item, ctr)
=>
+ ctr + (item -> (ctr(item) + 1))
--- End diff --
Use a mutable `Map` and then `ctr(item) += 1` here.
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