Jaro–Winkler distance algorithm in C#

Question

How would the Jaro–Winkler distance string comparison algorithm be implemented in C#?

Answer 1

public static class JaroWinklerDistance {     /* The Winkler modification will not be applied unless the       * percent match was at or above the mWeightThreshold percent       * without the modification.       * Winkler's paper used a default value of 0.7      */     private static readonly double mWeightThreshold = 0.7;      /* Size of the prefix to be concidered by the Winkler modification.       * Winkler's paper used a default value of 4      */     private static readonly int mNumChars = 4;       /// <summary>     /// Returns the Jaro-Winkler distance between the specified       /// strings. The distance is symmetric and will fall in the      /// range 0 (perfect match) to 1 (no match).      /// </summary>     /// <param name="aString1">First String</param>     /// <param name="aString2">Second String</param>     /// <returns></returns>     public static double distance(string aString1, string aString2) {         return 1.0 - proximity(aString1,aString2);     }       /// <summary>     /// Returns the Jaro-Winkler distance between the specified       /// strings. The distance is symmetric and will fall in the      /// range 0 (no match) to 1 (perfect match).      /// </summary>     /// <param name="aString1">First String</param>     /// <param name="aString2">Second String</param>     /// <returns></returns>     public static double proximity(string aString1, string aString2)     {         int lLen1 = aString1.Length;         int lLen2 = aString2.Length;         if (lLen1 == 0)             return lLen2 == 0 ? 1.0 : 0.0;          int  lSearchRange = Math.Max(0,Math.Max(lLen1,lLen2)/2 - 1);          // default initialized to false         bool[] lMatched1 = new bool[lLen1];         bool[] lMatched2 = new bool[lLen2];          int lNumCommon = 0;         for (int i = 0; i < lLen1; ++i) {             int lStart = Math.Max(0,i-lSearchRange);             int lEnd = Math.Min(i+lSearchRange+1,lLen2);             for (int j = lStart; j < lEnd; ++j) {                 if (lMatched2[j]) continue;                 if (aString1[i] != aString2[j])                     continue;                 lMatched1[i] = true;                 lMatched2[j] = true;                 ++lNumCommon;                 break;             }         }         if (lNumCommon == 0) return 0.0;          int lNumHalfTransposed = 0;         int k = 0;         for (int i = 0; i < lLen1; ++i) {             if (!lMatched1[i]) continue;             while (!lMatched2[k]) ++k;             if (aString1[i] != aString2[k])                 ++lNumHalfTransposed;             ++k;         }         // System.Diagnostics.Debug.WriteLine("numHalfTransposed=" + numHalfTransposed);         int lNumTransposed = lNumHalfTransposed/2;          // System.Diagnostics.Debug.WriteLine("numCommon=" + numCommon + " numTransposed=" + numTransposed);         double lNumCommonD = lNumCommon;         double lWeight = (lNumCommonD/lLen1                          + lNumCommonD/lLen2                          + (lNumCommon - lNumTransposed)/lNumCommonD)/3.0;          if (lWeight <= mWeightThreshold) return lWeight;         int lMax = Math.Min(mNumChars,Math.Min(aString1.Length,aString2.Length));         int lPos = 0;         while (lPos < lMax && aString1[lPos] == aString2[lPos])             ++lPos;         if (lPos == 0) return lWeight;         return lWeight + 0.1 * lPos * (1.0 - lWeight);      }   } 

Answer 2

You can take a look on Lucene.Net ,

it implement Jaro–Winkler distance algorithm ,

and its score is different from which leebickmtu post ,

you can take it as reference

the url is below :

http://lucenenet.apache.org/docs/3.0.3/db/d12/_jaro_winkler_distance_8cs_source.html