From 3c081da6511c161b80e42cbfc735aee68f61298d Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@ditigal.xyz>
Date: Sun, 26 Oct 2025 21:42:47 +0100
Subject: [PATCH] refactor: use evaluated population in selection

---
 env/src/selection.rs | 66 +++++++++++++++++++-------------------------
 1 file changed, 29 insertions(+), 37 deletions(-)

diff --git a/env/src/selection.rs b/env/src/selection.rs
index 8e83c69d0b67c205ab652dced5bc43631d354460..ea03a8746ad6015151cb26b71d19bc03940e4093 100644
--- a/env/src/selection.rs
+++ b/env/src/selection.rs
@@ -1,14 +1,13 @@
-// pub struct EvaluatedChromosome<TInput, TResult> {
-//     chromosome: TInput,
-//     evaluation: TResult,
-// }
+use rand::{seq::IteratorRandom, Rng, RngCore};
 
-use rand::{Rng, RngCore};
+use crate::{comparison::BetterThanOperator, replacement::EvaluatedPopulation};
 
-use crate::comparison::BetterThanOperator;
-
-pub trait Selection<T> {
-    fn select(&mut self, count: usize, evaluations: &Vec<T>, better_than: &dyn BetterThanOperator<T>) -> impl Iterator<Item = usize>;
+pub trait Selection<TChromosome, TResult> {
+    fn select(&mut self,
+              count: usize,
+              evaluations: &EvaluatedPopulation<TChromosome, TResult>,
+              better_than: &dyn BetterThanOperator<TResult>
+    ) -> impl Iterator<Item = usize>;
 }
 
 pub struct TournamentSelection {
@@ -29,8 +28,16 @@ impl TournamentSelection {
         }
     }
 
-    fn tournament<T: PartialOrd>(&mut self, idxs: &mut Vec<usize>, evaluations: &Vec<T>, better_than: &dyn BetterThanOperator<T>) -> usize {
-        idxs.sort_by(|&i, &j| better_than.ordering(&evaluations[i], &evaluations[j]));
+    fn tournament<TChromosome, TResult>(
+        &mut self,
+        idxs: &mut Vec<usize>,
+        evaluations: &EvaluatedPopulation<TChromosome, TResult>,
+        better_than: &dyn BetterThanOperator<TResult>
+    ) -> usize {
+        idxs.sort_by(|&i, &j| better_than.ordering(
+            &evaluations.population[i].evaluation,
+            &evaluations.population[j].evaluation)
+        );
 
         let mut p_selector = self.rng.random_range(0.0..=1.0f64);
         let p = self.p;
@@ -56,34 +63,19 @@ impl TournamentSelection {
     }
 }
 
-impl<T: Ord> Selection<T> for TournamentSelection {
-    fn select(&mut self, count: usize, evaluations: &Vec<T>, better_than: &dyn BetterThanOperator<T>) -> impl Iterator<Item = usize> {
-        // 1. Rank
-        // fn rank<T: Ord>(l: &Vec<T>) -> Vec<usize> {
-        //     let mut indices = (0..l.len()).collect::<Vec<_>>();
-        //     let mut ranks = vec![0; l.len()];
-
-        //     // argsort...
-        //     indices.sort_by_key(|&i| &l[i]);
-
-        //     for (rank, idx) in indices.into_iter().enumerate() {
-        //         ranks[idx] = rank;
-        //     }
-
-        //     ranks
-        // }
-
-        // let ranks = rank(evaluations);
-
-        // 2. Let's choose k random 'count' times
-        // let mut already_selected = vec![false; evaluations.len()];
-
+impl<TChromosome, TResult> Selection<TChromosome, TResult> for TournamentSelection {
+    fn select(
+        &mut self,
+        count: usize,
+        evaluations: &EvaluatedPopulation<TChromosome, TResult>,
+        better_than: &dyn BetterThanOperator<TResult>
+    ) -> impl Iterator<Item = usize> {
+        // Let's reuse a single vector for the indices
         let mut k_selected_idxs = vec![0; self.k];
         (0..count).map(move |_| {
-            for selected_idx in k_selected_idxs.iter_mut() {
-                *selected_idx = self.rng.random_range(0..evaluations.len());
-            }
-
+            // Choose k. Do not care if already selected previously.
+            (0..evaluations.population.len()).choose_multiple_fill(&mut self.rng, &mut k_selected_idxs);
+            // Tournament between the k
             self.tournament(&mut k_selected_idxs, evaluations, better_than)
         })
     }