Sean Owen commented on SPARK-21401:

I can't see how polling would be faster. When you poll you have to reheap and 
reassign elements of the queue. Whereas sorting can be done in-place, with 
native code and even in parallel, using quicksort. You do not show benchmarks 
of these two directly, and you're not replacing a sort anywhere. You may be 
measuring the cost of .toArray. I don't understand this and think it should be 

> 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
> 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.

This message was sent by Atlassian JIRA

To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org
For additional commands, e-mail: issues-h...@spark.apache.org

Reply via email to