Jenetics is an advanced Genetic Algorithm, respectively an Evolutionary Algorithm, library written in modern day Java.

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Currently v3.8.0

Jenetics is designed with a clear separation of the several concepts of the algorithm, e.g. Gene, Chromosome, Genotype, Phenotype, Population and fitness Function. Jenetics allows you to minimize and maximize the given fitness function without tweaking it. In contrast to other GA implementations, the library uses the concept of an evolution stream (EvolutionStream) for executing the evolution steps. Since the EvolutionStream implements the Java Stream interface, it works smoothly with the rest of the Java Stream API.

Features

Frictionless minimization

No need to tweak the fitness function for minimization problems. Just change the configuration of the evolution Engine.

Plugable PRNG

Easy changeable PRNG (RandomRegistry). No special PRNG interface; the standard Java Random engine allows the use of existing random generators.

Parallel processing support

Processing of the evolutionary steps can be executed in parallel!

Dependency free

No runtime dependencies to Third Party libraries! No mismatch and class loading problems with other libraries.

Java 8 ready

Fully support of Java 8 Streams and Lambdas!

Fully documented

Complete Documentation and User guide available, including documentation of selected implementation details.

Introduction

An excellent introduction is given by this Baeldung blog entry.

Examples

Hello World (Ones counting)

The minimum evolution Engine setup needs a genotype factory, Factory<Genotype<?>>, and a fitness Function. The Genotype implements the Factory interface and can therefore be used as prototype for creating the initial Population and for creating new random Genotypes.

import org.jenetics.BitChromosome;
import org.jenetics.BitGene;
import org.jenetics.Genotype;
import org.jenetics.engine.Engine;
import org.jenetics.engine.EvolutionResult;
import org.jenetics.util.Factory;

public class HelloWorld {
    // 2.) Definition of the fitness function.
    private static Integer eval(Genotype<BitGene> gt) {
        return gt.getChromosome()
            .as(BitChromosome.class)
            .bitCount();
    }

    public static void main(String[] args) {
        // 1.) Define the genotype (factory) suitable
        //     for the problem.
        Factory<Genotype<BitGene>> gtf =
            Genotype.of(BitChromosome.of(10, 0.5));

        // 3.) Create the execution environment.
        Engine<BitGene, Integer> engine = Engine
            .builder(HelloWorld::eval, gtf)
            .build();

        // 4.) Start the execution (evolution) and
        //     collect the result.
        Genotype<BitGene> result = engine.stream()
            .limit(100)
            .collect(EvolutionResult.toBestGenotype());

        System.out.println("Hello World:\n" + result);
    }
}
In contrast to other GA implementations, the library uses the concept of an evolution stream (EvolutionStream) for executing the evolution steps. Since the EvolutionStream implements the Java Stream interface, it works smoothly with the rest of the Java streaming API. Now let's have a closer look at listing above and discuss this simple program step by step:
  1. The probably most challenging part, when setting up a new evolution Engine, is to transform the problem domain into a appropriate Genotype (factory) representation. In our example we want to count the number of ones of a BitChromosome. Since we are counting only the ones of one chromosome, we are adding only one BitChromosome to our Genotype. In general, the Genotype can be created with 1 to n chromosomes.
  2. Once this is done, the fitness function which should be maximized, can be defined. Utilizing the new language features introduced in Java 8, we simply write a private static method, which takes the genotype we defined and calculate it's fitness value. If we want to use the optimized bit-counting method, bitCount(), we have to cast the Chromosome<BitGene> class to the actual used BitChromosome class. Since we know for sure that we created the Genotype with a BitChromosome, this can be done safely. A reference to the eval method is then used as fitness function and passed to the Engine.build method.
  3. In the third step we are creating the evolution Engine, which is responsible for changing, respectively evolving, a given population. The Engine is highly configurable and takes parameters for controlling the evolutionary and the computational environment. For changing the evolutionary behavior, you can set different alterers and selectors. By changing the used Executor service, you control the number of threads, the Engine is allowed to use. An new Engine instance can only be created via its builder, which is created by calling the Engine.builder method.
  4. In the last step, we can create a new EvolutionStream from our Engine. The EvolutionStream is the model or view of the evolutionary process. It serves as a »process handle« and also allows you, among other things, to control the termination of the evolution. In our example, we simply truncate the stream after 100 generations. If you don't limit the stream, the EvolutionStream will not terminate and run forever. Since the EvolutionStream extends the java.util.stream.Stream interface, it integrates smoothly with the rest of the Java Stream API. The final result, the best Genotype in our example, is then collected with one of the predefined collectors of the EvolutionResult class.

Evolving images

This example tries to approximate a given image by semitransparent polygons. It comes with an Swing UI, where you can immediately start your own experiments.

Evolving Mona Lisa

For a detailed description on how to execute this example, have a look at the Github project page.

Additional io.jenetics libraries

  • PRNGine: A pseudo-random number generator library for sequential and parallel Monte Carlo simulations. It has been designed to work smoothly with the Jenetics library, but it has no dependency to it. All PRNG implementations of this library extends the Java Random class, which makes it easily usable in other projects.
  • JPX: A Java library for creating, reading and writing GPS data in GPX format. It is a full implementation of version 1.1 of the GPX format. The data classes are completely immutable and allows a functional programming style. They are working also nicely with the Java 8 Stream API. Since it is also possible to calculate the distance between way-points, it is a good fit for the TSP.

Incubation modules

Projects using Jenetics

  • APP4MC: Eclipse APP4MC is a platform for engineering embedded multi- and many-core software systems.

Blogs

Citations

Used software