[jira] [Updated] (TEXT-131) JaroWinklerDistance: Calculation deviates from definition

["Pascal Schumacher (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TEXT-131?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Pascal Schumacher updated TEXT-131:
-----------------------------------
    Affects Version/s: 1.4

> JaroWinklerDistance: Calculation deviates from definition
> ---------------------------------------------------------
>
>                 Key: TEXT-131
>                 URL: https://issues.apache.org/jira/browse/TEXT-131
>             Project: Commons Text
>          Issue Type: Bug
>    Affects Versions: 1.4
>            Reporter: Jan Martin Keil
>            Assignee: Rob Tompkins
>            Priority: Major
>
> The calculation in {{JaroWinklerDistance}} deviates from the definition of the Jaro-Winkler Similarity. By definition the common prefix length is only determine for the first 4 characters. Further, the JaroWinkler is defined as {{JaroSimilarity + ScalingFactor * CommonPrefixLength * (1 - JaroSimilarity )}}.
>  Therefore, I recommend the following changes:
>  # Update Jaro-Winkler Similarity calculation
> {code:java}
> final double jw = j < 0.7D ? j : j + Math.min(defaultScalingFactor, 1D / mtp[3]) * mtp[2] * (1D - j);
> {code}
> to
> {code:java}
> final double jw = j < 0.7D ? j : j + defaultScalingFactor * mtp[2] * (1D - j);
> {code}
>  # Update calculation of Common Prefix Length
> {code:java}
> for (int mi = 0; mi < min.length(); mi++) {
> {code}
> to
> {code:java}
> for (int mi = 0; mi < Math.min(4, min.length()); mi++) {
> {code}
>  # Remove unnecessary return value
> {code:java}
> return new int[] {matches, transpositions, prefix, max.length()};
> {code}
> to
> {code:java}
> return new int[] {matches, transpositions, prefix};
> {code}



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