dictomaton
Introduction
This Java library implements dictionaries that are stored in finite state
automata. Dictomaton has the following features:
- Finite state dictionaries that implement the Java Set interface.
- Perfect hash dictionaries, that provide a unique hash for each character
sequence that is in the dictionary. Perfect hash dictionaries can be used
in two directions: (1) obtaining the hash code for a character sequence
and (2) obtaining the character sequence for a hash code.
- Levenshtein automata, that allow you to efficiently find all the sequences
in the dictionary that are within the given edit distance of a sequence.
- String to primitive type mappings, where the keys are stored in a perfect
hashing automaton and the values in an (unboxed) array.
Using Dictomaton
Dictomaton is in the Maven Central Repository:
<dependency>
<groupId>eu.danieldk.dictomaton</groupId>
<artifactId>dictomaton</artifactId>
<version>1.1.1</version>
</dependency>
SBT:
libraryDependencies += "eu.danieldk.dictomaton" % "dictomaton" % "1.1.1"
Grails:
compile 'eu.danieldk.dictomaton:dictomaton:1.1.1'
Comparisons
The following table compares the sizes of the object graphs of the
Dictionary type of this library to that of TreeSet and
HashSet. The comparisons were obtained by storing all the words
in the web2 and web2a dictionaries and were measured using
memory-measurer
| Data type | Objects | References | char | int | boolean | float |
|---|
| TreeSet | 936277 | 1872555 | 3193749 | 624184 | 312091 | 0 |
| HashSet | 936277 | 1772657 | 3193749 | 936277 | 1 | 1 |
| Dictionary | 41188 | 94546 | 424169 | 397033 | 1 | 1 |
Benchmarks
Benchmarks are in a different test group than normal unit tests. You can run
benchmarks via Maven, adding the Benchmarks group:
mvn test -Djunit.groups=eu.danieldk.dictomaton.categories.Benchmarks
Changelog
1.2.0
- Exposing state through StateInfo object, which allows user of PerfectHashDictionary to resume transitions, which makes it e.g. far more efficient to look up a string and its prefixes. (contributed by René Kriegler).
- DictionaryBuilder now accepts adding more general CharSequence instead of String and uses CharSequence internally (contributed by René Kriegler).
1.1.0
- Added immutable mapping from String to a generic type.
- Added a key-ordered builder for immutable mappings. This builder is more
efficient since it construct the key automaton on the fly.
1.0.0
- Added Levenshtein automata for looking up sequences in a Dictionary that
are within a certain edit distance of a sequence.
- Provide a variant of perfect hash automata that puts right language
cardinalities in transitions rather than states. This provides faster
hashing and hashcode lookups at the cost of some memory.
- Added String to String mapping (ImmutableStringStringMap).
- Generic object values.
0.0.3
- Fix an off-by-one error in integer width of the state table.
0.0.2
- Rename the project from fsadict-java to dictomaton.
- Store the state and transition tables as packed int arrays, resulting in drastically smaller automata.
Release plan
Plans for 1.3.0: Perhaps an explicit, fast, and compact data storage format
as an alternative to Java serialization. C or C++ version.
Contributors
- Daniël de Kok (maintainer)
- René Kriegler
