From 44fb8c9207de16114ae0b0017575ba6b94f3ecb6 Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@ditigal.xyz>
Date: Sat, 1 Nov 2025 14:24:24 +0100
Subject: [PATCH] feat(tsp): add cycle, no and partially mapped crossovers

---
 codes/tsp_hw01/src/crossovers.rs | 200 ++++++++++++++++++++++++++++++-
 1 file changed, 199 insertions(+), 1 deletion(-)

diff --git a/codes/tsp_hw01/src/crossovers.rs b/codes/tsp_hw01/src/crossovers.rs
index 27f1ae423935b4e081aed3a49261a3fca04c4c39..581dddd9effc6c3d4a116071d5be358abb1a5391 100644
--- a/codes/tsp_hw01/src/crossovers.rs
+++ b/codes/tsp_hw01/src/crossovers.rs
@@ -1,11 +1,45 @@
 use std::marker::PhantomData;
-use nalgebra::{allocator::Allocator, DefaultAllocator, Dim, Const, OMatrix, OVector};
+use nalgebra::{allocator::Allocator, Const, DefaultAllocator, Dim, OMatrix, OVector, U1};
 use rand::{prelude::IteratorRandom, Rng, RngCore};
 use eoa_lib::replacement::Population;
 use itertools::Itertools;
 use eoa_lib::crossover::Crossover;
 use crate::tsp::NodePermutation;
 
+pub struct NoCrossover<D> {
+    _phantom: PhantomData<D>
+}
+
+impl<D> NoCrossover<D> {
+    pub fn new() -> Self {
+        Self { _phantom: PhantomData }
+    }
+}
+
+impl<D> Crossover<2> for NoCrossover<D>
+where
+    D: Dim,
+    DefaultAllocator: Allocator<D>,
+{
+    type Chromosome = NodePermutation<D>;
+    type Out = f64;
+
+    fn crossover(
+        &self,
+        parents: &eoa_lib::replacement::EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        pairs: impl Iterator<Item = eoa_lib::pairing::ParentPairing<2>>,
+        _: &mut dyn RngCore
+    ) -> Population<Self::Chromosome> {
+        let mut offsprings = vec![];
+        for pair in pairs {
+            offsprings.push(parents.population[pair[0]].chromosome.clone());
+            offsprings.push(parents.population[pair[1]].chromosome.clone());
+        }
+
+        Population::from_vec(offsprings)
+    }
+}
+
 pub struct EdgeRecombinationCrossover<D> {
     _phantom: PhantomData<D>
 }
@@ -138,3 +172,167 @@ where
         Population::from_vec(offsprings)
     }
 }
+
+pub struct CycleCrossover<D: Dim> {
+    _phantom: PhantomData<D>
+}
+
+impl<D: Dim> CycleCrossover<D>
+where
+    D: Dim,
+    DefaultAllocator: Allocator<D>,
+{
+    pub fn new() -> Self {
+        Self { _phantom: PhantomData }
+    }
+
+    fn perform_crossover(
+        &self,
+        parent1: &OVector<usize, D>,
+        parent2: &OVector<usize, D>,
+        city_positions: &mut [usize]
+    ) -> NodePermutation<D> {
+        let mut offspring = parent2.clone();
+
+        for (i, &city) in parent1.iter().enumerate() {
+            city_positions[city] = i;
+        }
+
+        let mut i = 0;
+        let mut first = true;
+        while i != 0 || first {
+            first = false;
+
+            let city = parent1[i];
+
+            offspring[i] = city;
+
+            let city = parent2[i];
+            i = city_positions[city];
+        }
+
+        NodePermutation { permutation: offspring }
+    }
+}
+
+impl<D: Dim> Crossover<2> for CycleCrossover<D>
+where
+    D: Dim,
+    DefaultAllocator: Allocator<D>,
+{
+    type Chromosome = NodePermutation<D>;
+    type Out = f64;
+
+    fn crossover(
+        &self,
+        parents: &eoa_lib::replacement::EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        pairs: impl Iterator<Item = eoa_lib::pairing::ParentPairing<2>>,
+        rng: &mut dyn RngCore
+    ) -> Population<Self::Chromosome> {
+        let mut offsprings = vec![];
+
+        let permutation = &parents.population[0].chromosome.permutation;
+        let mut city_positions =
+            OVector::zeros_generic(permutation.shape_generic().0, U1);
+
+        for pair in pairs {
+            let parent1 = &parents.population[pair.x].chromosome;
+            let parent2 = &parents.population[pair.y].chromosome;
+
+            let (perm1, perm2) = (
+                &parent1.permutation,
+                &parent2.permutation
+            );
+
+            offsprings.push(self.perform_crossover(perm1, perm2, city_positions.as_mut_slice()));
+            offsprings.push(self.perform_crossover(perm2, perm1, city_positions.as_mut_slice()));
+        }
+
+        Population::from_vec(offsprings)
+    }
+}
+
+pub struct PartiallyMappedCrossover<D: Dim> {
+    _phantom: PhantomData<D>
+}
+
+impl<D: Dim> PartiallyMappedCrossover<D>
+where
+    D: Dim,
+    DefaultAllocator: Allocator<D>,
+{
+    pub fn new() -> Self {
+        Self { _phantom: PhantomData }
+    }
+
+    fn find_cross_points(&self, chromosome: &NodePermutation<D>, rng: &mut dyn RngCore) -> [usize; 2] {
+        let (min, max) = (0, chromosome.permutation.len());
+        let first = rng.random_range(min..max);
+        let second = rng.random_range(min..max);
+
+        [ first.min(second), first.max(second) ]
+    }
+
+    fn perform_crossover(
+        &self,
+        parent1: &OVector<usize, D>,
+        parent2: &OVector<usize, D>,
+        crossover_points: &[usize; 2],
+        city_positions: &mut [usize]
+    ) -> NodePermutation<D> {
+        let mut offspring = parent1.clone();
+
+        for (i, &city) in parent1.iter().enumerate() {
+            city_positions[city] = i;
+        }
+
+        for i in crossover_points[0]..crossover_points[1] {
+            let city = parent2[i];
+
+            offspring.swap_rows(
+                i,
+                city_positions[city]
+            );
+        }
+
+        NodePermutation { permutation: offspring }
+    }
+}
+
+impl<D: Dim> Crossover<2> for PartiallyMappedCrossover<D>
+where
+    D: Dim,
+    DefaultAllocator: Allocator<D>,
+{
+    type Chromosome = NodePermutation<D>;
+    type Out = f64;
+
+    fn crossover(
+        &self,
+        parents: &eoa_lib::replacement::EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        pairs: impl Iterator<Item = eoa_lib::pairing::ParentPairing<2>>,
+        rng: &mut dyn RngCore
+    ) -> Population<Self::Chromosome> {
+        let mut offsprings = vec![];
+
+        let permutation = &parents.population[0].chromosome.permutation;
+        let mut city_positions =
+            OVector::zeros_generic(permutation.shape_generic().0, U1);
+
+        for pair in pairs {
+            let parent1 = &parents.population[pair.x].chromosome;
+            let parent2 = &parents.population[pair.y].chromosome;
+
+            let (perm1, perm2) = (
+                &parent1.permutation,
+                &parent2.permutation
+            );
+
+            let cross_points = self.find_cross_points(parent1, rng);
+            offsprings.push(self.perform_crossover(perm1, perm2, &cross_points, city_positions.as_mut_slice()));
+            offsprings.push(self.perform_crossover(perm2, perm1, &cross_points, city_positions.as_mut_slice()));
+        }
+
+        Population::from_vec(offsprings)
+    }
+}