Levenshtein distance (v4)

Revision 4 of this benchmark created on

Setup

function levenshtein_distance_a(a, b) {
    if (a.length == 0) return b.length;
    if (b.length == 0) return a.length;
  
    var matrix = [];
  
    // increment along the first column of each row
    var i;
    for (i = 0; i <= b.length; i++) {
      matrix[i] = [i];
    }
  
    // increment each column in the first row
    var j;
    for (j = 0; j <= a.length; j++) {
      matrix[0][j] = j;
    }
  
    // Fill in the rest of the matrix
    for (i = 1; i <= b.length; i++) {
      for (j = 1; j <= a.length; j++) {
        if (b.charAt(i - 1) == a.charAt(j - 1)) {
          matrix[i][j] = matrix[i - 1][j - 1];
        } else {
          matrix[i][j] = Math.min(matrix[i - 1][j - 1] + 1, // substitution
          Math.min(matrix[i][j - 1] + 1, // insertion
          matrix[i - 1][j] + 1)); // deletion
        }
      }
    }
  
    return matrix[b.length][a.length];
  }
  
  // Heavily optimized... barely readable.
  
  
  function levenshtein_distance_b(a, b) {
    var lenA = a.length,
        lenB = b.length;
  
    if (!lenA) return lenB;
    if (!lenB) return lenA;
  
    var matrix = [];
  
    // increment along the first column of each row
    var i;
    for (i = 0; i <= lenB; i++) {
      matrix[i] = [i];
    }
  
    // increment each column in the first row
    var j;
    for (j = 0; j <= lenA; j++) {
      matrix[0][j] = j;
    }
  
    // Fill in the rest of the matrix
    var column, previous, prev, cost, letter;
  
    previous = matrix[0];
    letter = b[0];
    for (i = 1; i <= lenB; i++) {
      column = matrix[i];
      prev = previous[0];
  
      for (j = 1; j <= lenA; j++) {
        cost = previous[j];
        if (letter !== a[j - 1]) {
          // substitution, insertion, deletion
          prev = Math.min(prev, Math.min(column[j - 1], cost)) + 1;
        }
        column[j] = prev;
        prev = cost;
      }
  
      previous = column;
      letter = b[i];
    }
  
    return matrix[lenB][lenA];
  }

Test runner

Ready to run.

Testing in
TestOps/sec
algorithm A
levenshtein_distance_a('frankenstein', 'frankestein')
ready
algorithm B
levenshtein_distance_b('frankenstein', 'frankestein')
ready

Revisions

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