Jeffail / spiril

Rust library for genetic algorithms

Spiril

Spiril is an implementation of a genetic algorithm for obtaining optimum variables (genetics) for a task through mutation and natural selection.

The API allows you to specify an initial group of units, which will act as the original parents of all subsequent units. Unit types implement a fitness function and a breed function for introducing new genetic combinations and mutations into subsequent generations.

Fitnesses can be calculated across a population using parallel threads.

Sudoku example

extern crate spiril;
extern crate rand;

use spiril::unit::Unit;
use spiril::population::Population;
use rand::{StdRng, SeedableRng, Rng};

struct SudokuUnit {
    sudoku: Vec<usize>, // 9x9 grid
    answer: Vec<usize>, // 9x9 grid
}

impl Unit for SudokuUnit {
    fn fitness(&self) -> f64 {
        let mut score = 1.0_f64;

        for i in 0..9 {
            let mut seen_row: [usize; 9] = [0, 0, 0, 0, 0, 0, 0, 0, 0];
            let mut seen_col: [usize; 9] = [0, 0, 0, 0, 0, 0, 0, 0, 0];
            let mut seen_sqr: [usize; 9] = [0, 0, 0, 0, 0, 0, 0, 0, 0];

            for j in 0..9 {
                seen_row[self.answer[i * 9 + j] - 1] += 1;
                seen_col[self.answer[i + 9 * j] - 1] += 1;

                let sqr_index = ((i % 3) * 3) + (((i / 3) % 3) * 27) + (9 * (j / 3)) + j % 3;
                seen_sqr[self.answer[sqr_index] - 1] += 1;
            }

            seen_row
                .iter()
                .chain(seen_col.iter())
                .chain(seen_sqr.iter())
                .map(|x| if *x == 0 {
                    // score -= (1.0 / 729.0);
                    score *= 0.9;
                })
                .last();
        }

        score
    }

    fn breed_with(&self, other: &SudokuUnit) -> SudokuUnit {
        // Even rows taken from self, odd rows taken from other.
        // Mutations applied at random.
        let mut new_unit: SudokuUnit = SudokuUnit {
            sudoku: self.sudoku.clone(),
            answer: self.answer.clone(),
        };

        (0_usize..81_usize)
            .filter(|x| self.sudoku[*x] == 0)
            .map(|x| {
                if rand::thread_rng().gen_range(0, 1) == 1 {
                    new_unit.answer[x] = other.answer[x];
                }
                new_unit.answer[x]
            })
            .last();

        loop {
            let i = rand::thread_rng().gen_range(0, 81);
            if self.sudoku[i] == 0 {
                new_unit.answer[i] = rand::thread_rng().gen_range(1, 10);
                break;
            }
        }

        new_unit
    }
}

fn main() {
    let test_doku: Vec<usize> = vec![
        7, 2, 6,   0, 9, 3,   8, 1, 5,
        3, 0, 5,   7, 2, 8,   9, 0, 6,
        4, 8, 0,   6, 0, 1,   2, 3, 7,

        8, 5, 2,   1, 4, 0,   6, 9, 3,
        0, 7, 3,   9, 8, 5,   1, 2, 4,
        9, 4, 1,   0, 6, 2,   0, 5, 8,

        1, 9, 0,   8, 3, 0,   5, 7, 2,
        5, 6, 7,   2, 1, 4,   3, 8, 0,
        2, 0, 8,   5, 0, 9,   4, 6, 1,
    ];

    let seed: &[_] = &[0];
    let mut init_rng: StdRng = SeedableRng::from_seed(seed);
    let units: Vec<SudokuUnit> = (0..1000)
        .map(|_| {
            SudokuUnit {
                sudoku: test_doku.clone(),
                answer: test_doku
                    .clone()
                    .iter()
                    .map(|x| if *x == 0 {
                        init_rng.gen_range(1, 10)
                    } else {
                        *x
                    })
                    .collect(),
            }
        })
        .collect();

    assert_eq!(Population::new(units)
        .set_size(1000)
        .set_breed_factor(0.3)
        .set_survival_factor(0.5)
        .epochs_parallel(5000, 4) // 4 CPU cores
        .finish()
        .first()
        .unwrap()
        .fitness(), 1.0);
}