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https://issues.apache.org/jira/browse/SPARK-21401?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen resolved SPARK-21401.
-------------------------------
Resolution: Fixed
Fix Version/s: 2.3.0
Issue resolved by pull request 18620
[https://github.com/apache/spark/pull/18620]
> add poll function for BoundedPriorityQueue
> ------------------------------------------
>
> Key: SPARK-21401
> URL: https://issues.apache.org/jira/browse/SPARK-21401
> Project: Spark
> Issue Type: Improvement
> Components: ML, MLlib
> Affects Versions: 2.3.0
> Reporter: Peng Meng
> Priority: Minor
> Fix For: 2.3.0
>
>
> The most of BoundedPriorityQueue usages in ML/MLLIB are:
> Get the value of BoundedPriorityQueue, then sort it.
> For example, in Word2Vec: pq.toSeq.sortBy(-_._2)
> in ALS, pq.toArray.sorted()
> The test results show using pq.poll() is much faster than sort the value.
> For example, in PR https://github.com/apache/spark/pull/18624
> We get the sorted value of pq by the following code:
> {quote}
> var size = pq.size
> while(size > 0) {
> size -= 1
> val factor = pq.poll
> }{quote}
> If using the generally used methods: pq.toArray.sorted() to get the sorted
> value of pq. There is about 10% performance reduction.
> It is good to add the poll function for BoundedPriorityQueue, since many
> usages of PQ need the sorted value.
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