From b5a1a3a5c0d569ee3d8a87353fa2fc52ab634f88 Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@ditigal.xyz>
Date: Sun, 26 Oct 2025 21:42:37 +0100
Subject: [PATCH] feat: add crossover

---
 env/src/crossover.rs | 161 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 161 insertions(+)
 create mode 100644 env/src/crossover.rs

diff --git a/env/src/crossover.rs b/env/src/crossover.rs
new file mode 100644
index 0000000000000000000000000000000000000000..717c88304cdea7fbaf1bad8863d96cb549d8da11
--- /dev/null
+++ b/env/src/crossover.rs
@@ -0,0 +1,161 @@
+use std::marker::PhantomData;
+
+use nalgebra::{allocator::Allocator, DefaultAllocator, Dim, OVector, Scalar, U1};
+use rand::{Rng, RngCore};
+
+use crate::{binary_string::BinaryString, pairing::ParentPairing, replacement::{EvaluatedPopulation, Population}};
+
+pub trait Crossover {
+    type Chromosome;
+    type Out;
+
+    fn crossover(
+        &mut self,
+        parents: &EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        pairs: impl Iterator<Item = ParentPairing>
+    ) -> Population<Self::Chromosome>;
+}
+
+pub struct BinaryOnePointCrossover<D: Dim, TOutput> {
+    _phantom1: PhantomData<D>,
+    _phantom2: PhantomData<TOutput>,
+    rng: Box<dyn RngCore>
+}
+
+impl<D: Dim, TOutput> BinaryOnePointCrossover<D, TOutput>
+where
+    DefaultAllocator: Allocator<D>
+{
+    pub fn new() -> Self {
+        Self {
+            rng: Box::new(rand::rng()),
+            _phantom1: PhantomData,
+            _phantom2: PhantomData,
+        }
+    }
+
+    fn find_cross_point(&mut self, chromosome: &BinaryString<D>) -> usize {
+        let (min, max) = (0, chromosome.vec.len());
+        self.rng.random_range(min..max)
+    }
+}
+
+// TODO: make common functions for ovector that will be used from both BinaryOnePointCrossover and OVectorOnePointCrossover
+// for not repeating the code.
+
+impl<D, TOutput> Crossover for BinaryOnePointCrossover<D, TOutput>
+where
+    D: Dim,
+    DefaultAllocator: Allocator<D>
+{
+    type Chromosome = BinaryString<D>;
+    type Out = TOutput;
+
+    fn crossover(
+        &mut self,
+        population: &EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        pairs: impl Iterator<Item = ParentPairing>
+    ) -> Population<Self::Chromosome> {
+
+        let chromosome = &population.population[0].chromosome.vec;
+        let len = population.population[0].chromosome.vec.len();
+        let indices = OVector::<usize, D>::from_iterator_generic(chromosome.shape_generic().0, U1, 0..len);
+
+        let mut offsprings = Vec::new();
+        for pair in pairs {
+            let (
+                parent1,
+                parent2
+            ) = (&population.population[pair.0], &population.population[pair.1]);
+
+            let (
+                chromosome1,
+                chromosome2
+            ) = (&parent1.chromosome, &parent2.chromosome);
+
+            let cross_point = self.find_cross_point(&population.population[0].chromosome);
+
+            offsprings.push(BinaryString::from_ovector(
+                chromosome1.vec.zip_zip_map(
+                    &chromosome2.vec,
+                    &indices,
+                    |first, second, i| if i <= cross_point { first } else { second }
+                )));
+        }
+
+        Population::from_vec(offsprings)
+    }
+}
+
+
+pub struct OVectorOnePointCrossover<D: Dim, T: Scalar, TOutput> {
+    _phantom1: PhantomData<D>,
+    _phantom2: PhantomData<TOutput>,
+    _phantom3: PhantomData<T>,
+    rng: Box<dyn RngCore>
+}
+
+impl<D: Dim, T, TOutput> OVectorOnePointCrossover<D, T, TOutput>
+where
+    T: Scalar,
+    DefaultAllocator: Allocator<D>
+{
+    pub fn new() -> Self {
+        Self {
+            rng: Box::new(rand::rng()),
+            _phantom1: PhantomData,
+            _phantom2: PhantomData,
+            _phantom3: PhantomData,
+        }
+    }
+
+    fn find_cross_point(&mut self, chromosome: &OVector<T, D>) -> usize {
+        let (min, max) = (0, chromosome.len());
+        self.rng.random_range(min..max)
+    }
+}
+
+impl<D, T, TOutput> Crossover for OVectorOnePointCrossover<D, T, TOutput>
+where
+    T: Scalar,
+    D: Dim,
+    DefaultAllocator: Allocator<D>
+{
+    type Chromosome = OVector<T, D>;
+    type Out = TOutput;
+
+    fn crossover(
+        &mut self,
+        population: &EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        pairs: impl Iterator<Item = ParentPairing>
+    ) -> Population<Self::Chromosome> {
+
+        let chromosome = &population.population[0].chromosome;
+        let len = population.population[0].chromosome.len();
+        let indices = OVector::<usize, D>::from_iterator_generic(chromosome.shape_generic().0, U1, 0..len);
+
+        let mut offsprings = Vec::new();
+        for pair in pairs {
+            let (
+                parent1,
+                parent2
+            ) = (&population.population[pair.0], &population.population[pair.1]);
+
+            let (
+                chromosome1,
+                chromosome2
+            ) = (&parent1.chromosome, &parent2.chromosome);
+
+            let cross_point = self.find_cross_point(&population.population[0].chromosome);
+
+            offsprings.push(
+                chromosome1.zip_zip_map(
+                    &chromosome2,
+                    &indices,
+                    |first, second, i| if i <= cross_point { first } else { second }
+                ));
+        }
+
+        Population::from_vec(offsprings)
+    }
+}