Crate rsgenetic

RsGenetic

RsGenetic provides a simple framework for genetic algorithms. You need to provide the definition of a Phenotype (also known as an Individual), define how crossover and mutation work, present a fitness function, choose some settings and this library takes care of the rest.

Installation

You can use this library by adding the following lines to your Cargo.toml file:

[dependencies]
rsgenetic = "^1.8.0"

and adding extern crate rsgenetic; to your crate root.

Features

Available Simulators

There is currently only one, sequential, simulator. This simulator will run the genetic algorithm on a single thread.

Available Selection Types

There are currently four selection types available:

• Maximize
• Tournament
• Stochastic

There is a short explanation for each of these below. For more information, look at the documentation of individual selectors.

Maximize

Maximize takes 1 parameter: the count. This is half the number of parents that will be selected. Selection happens by taking the top count individuals, ranked by fitness. The resulting number of parents is count.

Tournament

Tournament takes 2 parameters: the number of tournaments (count) and participators, which indicates how many phenotypes participate in a tournament. The resulting number of parents is count.

Stochastic

Stochastic takes 1 parameter: the count. The resulting number of parents is count.

Early Stopping

If you wish, you can stop early if the fitness value of the best performing Phenotype doesn’t improve by a large amount for a number of iterations. This can be done by calling the set_early_stop(delta: Fitness, n_iters: u32) function on the SimulatorBuilder.

Examples

Implementing the Fitness trait

Note that, if your fitness type is an integer type, you do not need to write a wrapper struct around this integer. See the types module documentation for more details.

use rsgenetic::pheno::*;
use std::cmp::Ordering;

#[derive(Eq, PartialEq, PartialOrd, Ord)]
struct MyFitness {
    value: i32,
}

impl Fitness for MyFitness {
    // The zero value for our custom type
    fn zero() -> MyFitness {
        MyFitness { value: 0 }
    }

    // The absolute difference between two instances
    fn abs_diff(&self, other: &MyFitness) -> MyFitness {
        MyFitness {
            value: (self.value - other.value).abs()
        }
    }
}

Implementing the Phenotype trait

Note that we use an integer type as the fitness type parameter to make this example more simple. Replace it with your custom type if needed. In this example, we try to find individuals with two integer components that sum to a target value.

This example is far-fetched, but simplified to show how easy it is to define new individuals and implement the Phenotype trait.

use rsgenetic::pheno::*;

const TARGET: i32 = 100;

#[derive(Copy, Clone)]
struct MyPheno {
    x: i32,
    y: i32,
}

impl Phenotype<i32> for MyPheno {
    // How fit is this individual?
    fn fitness(&self) -> i32 {
        TARGET - (self.x + self.y)
    }

    // Have two individuals create a new individual
    fn crossover(&self, other: &MyPheno) -> MyPheno {
        MyPheno {
            x: self.x,
            y: other.y,
        }
    }

    // Mutate an individual, changing its state
    fn mutate(&self) -> MyPheno {
        MyPheno {
            x: self.x + 1,
            y: self.y - 1,
        }
    }
}

Creating and running a Simulator

use rsgenetic::sim::*;
use rsgenetic::sim::seq::Simulator;
use rsgenetic::sim::select::*;

// (Assuming the above definition of `MyPheno` is in scope)
// [ ... ]

fn main() {
    let mut population = (0..100).map(|i| MyPheno { x: i, y: 100 - i }).collect();
    let mut s = Simulator::builder(&mut population)
                    .set_selector(Box::new(StochasticSelector::new(10)))
                    .set_max_iters(50)
                    .build();
    s.run();
    let result = s.get().unwrap(); // The best individual
}

See the examples directory in the repository for more elaborate examples.

Modules

pheno

Contains the definition of a Phenotype.

sim

Contains implementations of Simulators, which can run genetic algorithms.