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Fast Ruby FFI string edit distance algorithms
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Hotwater v0.1.2

build status

Ruby & JRuby gem with fast string edit distance algorithms C implementations with FFI bindings.



Tested on OSX 10.8.2 and Linux 12.10 with

  • MRI Ruby 1.9.3 p385
  • JRuby 1.7.2 (1.9.3 p327)

Add this line to your application's Gemfile:

gem 'hotwater'

And then execute:

$ bundle

Or install it yourself as:

$ gem install hotwater


Hotwater.levenshtein_distance("abc", "acb") # => 2
Hotwater.damerau_levenshtein_distance("abc", "acb") # => 1

# normalization based on the string sizes
# where an edit on a small string has more weight than on a longer string
Hotwater.normalized_levenshtein_distance("abc", "acb").round(4) # => 0.3333
Hotwater.normalized_damerau_levenshtein_distance("abc", "acb").round(4) # => 0.6667

Hotwater.jaro_distance("martha", "marhta").round(4) # => 0.9444
Hotwater.jaro_winkler_distance("martha", "marhta").round(4) # => 0.9611

# default is bigram
Hotwater.ngram_distance("natural", "contrary").round(4) # => 0.25

# specify trigram
Hotwater.ngram_distance("natural", "contrary", 3).round(4) # => 0.2083


  1. Fort it
  2. Install gems $ bundle install
  3. Compile lib $ rake compile
  4. Run specs $ rake spec
  5. Clean compiler generated files $ rake clean


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request



Why Hotwater? as stated in the credits section, some of the C code comes from the jellyfish Python project. Jelly fish made me think right away about New Brunswick beaches where I have been a couple of times in the past years. There is this legend about New Brunswick having warm water beaches. I even saw a tourism promotion TV commercial selling NB as having warm water. This is a lie! :P I never experienced warm water (in the generaly accepted definition) in NB, only lots of jellyfish :D (that being said, I have enjoyed every bit of my visits in New Brunswick and I really do not care about warm water really ;)


Colin Surprenant, @colinsurprenant,,


Hotwater is distributed under the Apache License, Version 2.0.

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