NIF for Levenshtein distance
Switch branches/tags
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
c_src
src
.gitignore
LICENSE
README.md
rebar.config

README.md

Erlang Levenshtein Distance NIF

Native C implementation of the Levenshtein edit distance, easily importable into your Erlang project using rebar.

Add as a dependency:

{levenshtein, "0.6.0", {git, "https://github.com/rschlaikjer/erlang-levenshtein.git", {tag, "0.6.0"}}}

On a simple test case, this NIF performs multiple orders of magnitude better than a pure erlang implementation.

Eshell V8.2.1  (abort with ^G)
1> c('src/perftest').
{ok,perftest}
2> perftest:perftest(100000, fun perftest:erlang_perftest_loop/1).
204.19880963957932
3> perftest:perftest(100000, fun perftest:native_perftest_loop/1).
284196.46062523685

Test code:

-module(perftest).
-export([
    perftest/2,
    native_perftest_loop/1,
    erlang_perftest_loop/1
]).

perftest(Iterations, Method) ->
    Start = os:system_time(),
    Method(Iterations),
    Diff = os:system_time() - Start,
    (Iterations / Diff) * 1000000000.

native_perftest_loop(0) -> ok;
native_perftest_loop(I) ->
    levenshtein:levenshtein(
        <<"7ab02d24-2d67-11e8-835d-0b1d27744c6d">>,
        <<"80393ca4-2d67-11e8-8f7f-c7a8488e4904">>
    ),
    native_perftest_loop(I - 1).

erlang_perftest_loop(0) -> ok;
erlang_perftest_loop(I) ->
    erlang_leven(
        <<"7ab02d24-2d67-11e8-835d-0b1d27744c6d">>,
        <<"80393ca4-2d67-11e8-8f7f-c7a8488e4904">>
    ),
    erlang_perftest_loop(I - 1).

erlang_leven(<<Bin/binary>>, <<Bin2/binary>>) ->
    {Ed, _Cache} = erlang_leven(Bin, Bin2, dict:new()),
    Ed.

erlang_leven(<<>>, <<Bin/binary>>, Cache) ->
    {byte_size(Bin), dict:store({<<>>, Bin}, byte_size(Bin), Cache)};
erlang_leven(<<Bin/binary>>, <<"">>, Cache) ->
    {byte_size(Bin), dict:store({Bin, <<>>}, byte_size(Bin), Cache)};
erlang_leven(<<B:8, B1/binary>>, <<B:8, B2/binary>>, Cache) ->
    erlang_leven(B1, B2, Cache);
erlang_leven(Bin1 = <<_:8, B1/binary>>, Bin2 = <<_:8, B2/binary>>, Cache) ->
    case dict:is_key({Bin1, Bin2}, Cache) of
        true -> {dict:fetch({Bin1, Bin2}, Cache), Cache};
        false ->
            {L1, C1} = erlang_leven(Bin1, B2, Cache),
            {L2, C2} = erlang_leven(B1, Bin2, C1),
            {L3, C3} = erlang_leven(B1, B2, C2),
            L = 1 + lists:min([L1, L2, L3]),
            {L, dict:store({Bin1, Bin2}, L, C3)}
    end.

License

Copyright 2018 Ross Schlaikjer

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.