[jira] Commented: (MAHOUT-230) Replace org.apache.mahout.math.Sorting with code of clear provenance

[Robin Anil (JIRA)]

    [ 
https://issues.apache.org/jira/browse/MAHOUT-230?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12795047#action_12795047
 ] 

Robin Anil commented on MAHOUT-230:
-----------------------------------

I ran the SortingTest instead of 3.2 sec it now takes 5.2 seconds. I repeated 
the patch and rechecked. Any idea why the perf dip?  Notice the perf drop in 
the second block  i.e. after the line break in each block

{code:xml|title=Original Output} 

  <testcase time="0.016" classname="org.apache.mahout.math.SortingTest" 
name="testBinarySearch"/>
  <testcase time="0.015" classname="org.apache.mahout.math.SortingTest" 
name="testBinarySearchObjects"/>
  <testcase time="0.032" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortBytes"/>
  <testcase time="0.234" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortChars"/>
  <testcase time="0.188" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortInts"/>
  <testcase time="0.171" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortLongs"/>
  <testcase time="0.204" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortShorts"/>
  <testcase time="0.218" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortFloats"/>
  <testcase time="0.235" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortDoubles"/>
  <testcase time="0.062" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortBytes"/>

  <testcase time="0.313" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortChars"/>
  <testcase time="0.281" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortInts"/>
  <testcase time="0.391" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortLongs"/>
  <testcase time="0.25" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortShorts"/>
  <testcase time="0.359" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortFloats"/>
  <testcase time="0.328" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortDoubles"/>
{code} 

{code:xml|title=After Patching} 

  <testcase time="0.031" classname="org.apache.mahout.math.SortingTest" 
name="testBinarySearch"/>
  <testcase time="0" classname="org.apache.mahout.math.SortingTest" 
name="testBinarySearchObjects"/>
  <testcase time="0" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortBytes"/>
  <testcase time="0.234" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortChars"/>
  <testcase time="0.234" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortInts"/>
  <testcase time="0.172" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortLongs"/>
  <testcase time="0.266" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortShorts"/>
  <testcase time="0.235" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortFloats"/>
  <testcase time="0.25" classname="org.apache.mahout.math.SortingTest" 
name="testQuickSortDoubles"/>
  <testcase time="0.015" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortBytes"/>

  <testcase time="0.594" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortChars"/>
  <testcase time="0.61" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortInts"/>
  <testcase time="0.781" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortLongs"/>
  <testcase time="0.562" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortShorts"/>
  <testcase time="0.578" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortFloats"/>
  <testcase time="0.61" classname="org.apache.mahout.math.SortingTest" 
name="testMergeSortDoubles"/>
{code} 

> Replace org.apache.mahout.math.Sorting with code of clear provenance
> --------------------------------------------------------------------
>
>                 Key: MAHOUT-230
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-230
>             Project: Mahout
>          Issue Type: Bug
>          Components: Math
>    Affects Versions: 0.3
>            Reporter: Benson Margulies
>            Assignee: Benson Margulies
>             Fix For: 0.3
>
>         Attachments: replace-sorting.diff
>
>   Original Estimate: 72h
>  Remaining Estimate: 72h
>
> org.apache.mahout.math.Sorting looks as if the original author borrowed from 
> the Sun JRE, based on the private internal function names and contents. That 
> code has a restrictive license. We need to take the equivalent file 
> (java.util.Arrays) from Apache Harmony and use it as the basis for a clean 
> replacement.
> The problematic code are the quickSort and mergeSort functions, which extend 
> 'Arrays' by supporting slices of arrays and custom sorting predicate 
> functions. 
> One might also wistfully note that the more recent JDKs from Sun have 
> deployed different (and one hopes) better sort algorithms that 1.5 and/or 
> Harmony, so a really energetic person might build implementations in here to 
> match. However, expediency calls for just bashing on the Harmony 
> implementation to solve the problem at hand.

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