From 8b73ac0a6cd9d2d1ea618f9325fb59a74c5628ac Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@ditigal.xyz>
Date: Sun, 30 Nov 2025 18:33:27 +0100
Subject: [PATCH] feat: add bounded crossover similar to bounded perturbation

---
 codes/eoa_lib/src/crossover.rs | 112 +++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)

diff --git a/codes/eoa_lib/src/crossover.rs b/codes/eoa_lib/src/crossover.rs
index 7fc08373939a5d1249de75a1f03f5ede976355ef..ebd1c109d0f9d1740a396be849e6348530e37343 100644
--- a/codes/eoa_lib/src/crossover.rs
+++ b/codes/eoa_lib/src/crossover.rs
@@ -455,3 +455,115 @@ where
         Population::from_vec(offsprings)
     }
 }
+
+pub enum BoundedCrossoverStrategy {
+    /// Trims offspring values to get values within bounds
+    Trim,
+    /// Retries calling the underlying crossover until offspring within bounds is returned.
+    /// If argument is given, this is the maximum number of retries to do and then
+    /// fall back to trimming. Zero means retry indefinitely.
+    Retry(usize)
+}
+
+pub struct BoundedCrossover<D: Dim, const DParents: usize, T: Crossover<DParents, Chromosome = OVector<f64, D>>>
+where
+    DefaultAllocator: Allocator<D>
+{
+    min_max: OVector<(f64, f64), D>,
+    strategy: BoundedCrossoverStrategy,
+    crossover: T,
+    _phantom: PhantomData<fn() -> [(); DParents]>
+}
+
+impl<D: Dim, const DParents: usize, T: Crossover<DParents, Chromosome = OVector<f64, D>>> BoundedCrossover<D, DParents, T>
+where
+    DefaultAllocator: Allocator<D>
+{
+    pub fn new(
+        crossover: T,
+        min: OVector<f64, D>,
+        max: OVector<f64, D>,
+        strategy: BoundedCrossoverStrategy
+    ) -> Self {
+        let min_max = min.zip_map(&max, |min, max| (min, max));
+        Self {
+            min_max,
+            strategy,
+            crossover,
+            _phantom: PhantomData
+        }
+    }
+
+    fn within_bounds(&self, chromosome: &OVector<f64, D>) -> bool {
+        chromosome.iter()
+            .zip(self.min_max.iter())
+            .all(|(&c, &(min, max))| c <= max && c >= min)
+    }
+
+    fn bound(&self, mut chromosome: OVector<f64, D>) -> OVector<f64, D> {
+        chromosome
+            .zip_apply(&self.min_max, |c, (min, max)| *c = c.clamp(min, max));
+        chromosome
+    }
+
+    fn bound_population(&self, mut population: Population<OVector<f64, D>>) -> Population<OVector<f64, D>> {
+        for chromosome in population.iter_mut() {
+            *chromosome = self.bound(chromosome.clone());
+        }
+        population
+    }
+
+    fn all_within_bounds(&self, population: &Population<OVector<f64, D>>) -> bool {
+        population.iter().all(|chromosome| self.within_bounds(chromosome))
+    }
+
+    fn retry_crossover<TOut>(
+        &self,
+        population: &EvaluatedPopulation<OVector<f64, D>, TOut>,
+        pairs: Vec<ParentPairing<DParents>>,
+        retries: Option<usize>,
+        rng: &mut dyn RngCore
+    ) -> Population<OVector<f64, D>>
+    where
+        T: Crossover<DParents, Chromosome = OVector<f64, D>, Out = TOut>
+    {
+        let offspring = self.crossover.crossover(population, pairs.clone().into_iter(), rng);
+
+        if self.all_within_bounds(&offspring) {
+            return offspring;
+        }
+
+        match retries {
+            Some(0) | None => self.bound_population(offspring),
+            Some(retries) => {
+                self.retry_crossover(population, pairs, Some(retries - 1), rng)
+            }
+        }
+    }
+}
+
+impl<D: Dim, const DParents: usize, T, TOut> Crossover<DParents> for BoundedCrossover<D, DParents, T>
+where
+    T: Crossover<DParents, Chromosome = OVector<f64, D>, Out = TOut>,
+    DefaultAllocator: Allocator<D>
+{
+    type Chromosome = OVector<f64, D>;
+    type Out = TOut;
+
+    fn crossover(
+        &self,
+        population: &EvaluatedPopulation<Self::Chromosome, Self::Out>,
+        pairs: impl Iterator<Item = ParentPairing<DParents>>,
+        rng: &mut dyn RngCore
+    ) -> Population<Self::Chromosome> {
+        match self.strategy {
+            BoundedCrossoverStrategy::Trim => {
+                self.bound_population(self.crossover.crossover(population, pairs, rng))
+            },
+            BoundedCrossoverStrategy::Retry(retries) => {
+                let pairs_vec: Vec<_> = pairs.collect();
+                self.retry_crossover(population, pairs_vec, Some(retries), rng)
+            }
+        }
+    }
+}