jaro_winkler is an implementation of Jaro-Winkler similarity algorithm which is written in C extension and will fallback to pure Ruby version in platforms other than MRI/KRI like JRuby or Rubinius. Both of C and Ruby implementation support any kind of string encoding, such as UTF-8, EUC-JP, Big5, etc.

Installation

gem install jaro_winkler

Usage

require 'jaro_winkler'

# Jaro Winkler Similarity

JaroWinkler.similarity "MARTHA", "MARHTA"
# => 0.9611
JaroWinkler.similarity "MARTHA", "marhta", ignore_case: true
# => 0.9611
JaroWinkler.similarity "MARTHA", "MARHTA", weight: 0.2
# => 0.9778

# Jaro Similarity

JaroWinkler.jaro_similarity "MARTHA", "MARHTA"
# => 0.9444444444444445

There is no JaroWinkler.jaro_winkler_similarity, it's tediously long.

Options

Adjusting Table

Default Table

['A', 'E'], ['A', 'I'], ['A', 'O'], ['A', 'U'], ['B', 'V'], ['E', 'I'], ['E', 'O'], ['E', 'U'], ['I', 'O'], ['I', 'U'],
['O', 'U'], ['I', 'Y'], ['E', 'Y'], ['C', 'G'], ['E', 'F'], ['W', 'U'], ['W', 'V'], ['X', 'K'], ['S', 'Z'], ['X', 'S'],
['Q', 'C'], ['U', 'V'], ['M', 'N'], ['L', 'I'], ['Q', 'O'], ['P', 'R'], ['I', 'J'], ['2', 'Z'], ['5', 'S'], ['8', 'B'],
['1', 'I'], ['1', 'L'], ['0', 'O'], ['0', 'Q'], ['C', 'K'], ['G', 'J'], ['E', ' '], ['Y', ' '], ['S', ' ']

How it works?

Original Formula:

where

• m is the number of matching characters.
• t is half the number of transpositions.

With Adjusting Table:

where

• s is the number of nonmatching but similar characters.

Why This?

There is also another similar gem named fuzzy-string-match which both provides C and Ruby version as well.

I reinvent this wheel because of the naming in fuzzy-string-match such as getDistance breaks convention, and some weird code like a1 = s1.split( // ) (s1.chars could be better), furthermore, it's bugged (see tables below).

Compare with other gems

I made a table below to compare accuracy between each gem:

• The "origin" result is from the original C implementation by the author of the algorithm.
• Test data are borrowed from fuzzy-string-match's rspec file.

Benchmark

$ bundle exec rake benchmark
ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]

# C Extension
Rehearsal --------------------------------------------------------------
jaro_winkler (8c16e09)       0.240000   0.000000   0.240000 (  0.241347)
fuzzy-string-match (1.0.1)   0.400000   0.010000   0.410000 (  0.403673)
hotwater (0.1.2)             0.250000   0.000000   0.250000 (  0.254503)
amatch (0.4.0)               0.870000   0.000000   0.870000 (  0.875930)
----------------------------------------------------- total: 1.770000sec

                                 user     system      total        real
jaro_winkler (8c16e09)       0.230000   0.000000   0.230000 (  0.236921)
fuzzy-string-match (1.0.1)   0.380000   0.000000   0.380000 (  0.381942)
hotwater (0.1.2)             0.250000   0.000000   0.250000 (  0.254977)
amatch (0.4.0)               0.860000   0.000000   0.860000 (  0.861207)

# Pure Ruby
Rehearsal --------------------------------------------------------------
jaro_winkler (8c16e09)       0.440000   0.000000   0.440000 (  0.438470)
fuzzy-string-match (1.0.1)   0.860000   0.000000   0.860000 (  0.862850)
----------------------------------------------------- total: 1.300000sec

                                 user     system      total        real
jaro_winkler (8c16e09)       0.440000   0.000000   0.440000 (  0.439237)
fuzzy-string-match (1.0.1)   0.910000   0.010000   0.920000 (  0.920259)

Todo

• Custom adjusting word table.