DO NOT REPLY [Bug 31882] New: - [PATCH] FuzzyTermEnum optimization and refactor

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http://issues.apache.org/bugzilla/show_bug.cgi?id=31882

[PATCH] FuzzyTermEnum optimization and refactor

           Summary: [PATCH] FuzzyTermEnum optimization and refactor
           Product: Lucene
           Version: CVS Nightly - Specify date in submission
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Enhancement
          Priority: Other
         Component: Search
        AssignedTo: lucene-dev@jakarta.apache.org
        ReportedBy: jhager@gmail.com


I took a look at it to see if it could be improved.  I saw speed improvements of
20% - 40% by making a couple changes.  

The patch is here: http://www.hagerfamily.com/patches/FuzzyTermEnumOptimizePatch.txt

The Patch is based on the HEAD of the CVS tree as of Oct 22, 2004.

What Changed?

Since the word was discarded if the edit distance for the word was
above a certain threshold, I updated the distance algorithm to abort
if at any time during the calculation it is determined that the best
possible outcome of the edit distance algorithm is above this
threshold.  The source code has a great explanation.

I also reduced the amount of floating point math, reduced the amount
of potential space the array takes in its first dimension, removed the
potential divide by 0 error when one term is an empty string, and
fixed a bug where an IllegalArgumentException was thrown if the class
was somehow initialized wrong, instead of looking at the arguments.

The behavior is almost identical.  The exception is that similarity is
set to 0.0 when it is guaranteed to be below the minimum similarity.

Results

I saw the biggest improvement from longer words, which makes a sense.
My long word was "bridgetown" and I saw a 60% improvement on this.
The biggest improvement are for words that are farthest away from the
median length of the words in the index.  Short words (1-3 characters)
saw a 30% improvement.  Medium words saw a 10% improvement (5-7
characters).  These improvements are with the prefix set to 0.

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