DO NOT REPLY [Bug 48259] New: Improve StatCalculator performance by using HashMap

https://issues.apache.org/bugzilla/show_bug.cgi?id=48259

           Summary: Improve StatCalculator performance by using HashMap
           Product: JMeter
           Version: Nightly (Please specify date)
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Main
        AssignedTo: [email protected]
        ReportedBy: [email protected]


Created an attachment (id=24582)
 --> (https://issues.apache.org/bugzilla/attachment.cgi?id=24582)
Use HashMap for keeping values distribution instead of ArrayList

There is no actually need to store *each* value separately in StatCalculator
class. It's enough to save only counter of occurrences for every value. I
propose HashMap class for that instead of ArrayList.

HashMap provides several major benefits:
 - It occupies less memory than ArrayList, especially for large data sets,
because every inserted value will be kept within just one pair (key-value).
 - It has faster data insert (there is no need to call
Collections.binarySearch() for every addValue(), insert into HashMap has O(1)
complexity)
 - It still stays quite fast for reading. It calls for sorting in modified
getPercentPoint() method, but sorts only keys. A number of unique keys is
usually much less than total count of inserted values.

Sorry, I didn't check modified StatCalculator on real data yet, just run JMeter
tests. I will do it after the weekend. But I think it will work fine.

I worked at SVN build 883037.

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