From 0047990b459b29545707dbf614b37ae3b083e492 Mon Sep 17 00:00:00 2001
From: Rutherther <rutherther@ditigal.xyz>
Date: Mon, 27 Oct 2025 20:45:10 +0100
Subject: [PATCH] fix: return proper indices from tournament

---
 codes/eoa_lib/src/selection.rs | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/codes/eoa_lib/src/selection.rs b/codes/eoa_lib/src/selection.rs
index ea03a8746ad6015151cb26b71d19bc03940e4093..48718b9d62374591cf51cae11eaa9aabadedf0dc 100644
--- a/codes/eoa_lib/src/selection.rs
+++ b/codes/eoa_lib/src/selection.rs
@@ -1,4 +1,5 @@
 use rand::{seq::IteratorRandom, Rng, RngCore};
+use std::fmt::Debug;
 
 use crate::{comparison::BetterThanOperator, replacement::EvaluatedPopulation};
 
@@ -28,13 +29,13 @@ impl TournamentSelection {
         }
     }
 
-    fn tournament<TChromosome, TResult>(
+    fn tournament<TChromosome, TResult: Debug + Copy>(
         &mut self,
         idxs: &mut Vec<usize>,
         evaluations: &EvaluatedPopulation<TChromosome, TResult>,
         better_than: &dyn BetterThanOperator<TResult>
     ) -> usize {
-        idxs.sort_by(|&i, &j| better_than.ordering(
+        idxs.sort_unstable_by(|&i, &j| better_than.ordering(
             &evaluations.population[i].evaluation,
             &evaluations.population[j].evaluation)
         );
@@ -59,11 +60,11 @@ impl TournamentSelection {
             p_selector /= 1.0 - p;
         }
 
-        selected
+        idxs[selected]
     }
 }
 
-impl<TChromosome, TResult> Selection<TChromosome, TResult> for TournamentSelection {
+impl<TChromosome, TResult: Copy + Debug> Selection<TChromosome, TResult> for TournamentSelection {
     fn select(
         &mut self,
         count: usize,
@@ -76,7 +77,8 @@ impl<TChromosome, TResult> Selection<TChromosome, TResult> for TournamentSelecti
             // 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)
+            let index = self.tournament(&mut k_selected_idxs, evaluations, better_than);
+            index
         })
     }
 }