Remove reference_id from Chromosome

Author: basvanwesting

CHANGELOG.md

@@ -65,6 +65,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   top-parents is crucial for driving the Evolve process as experimenting with
   the evolve_nqueens example demonstrated.
 
+### Removed
+* Remove `reference_id: usize` from `Chromosome` as user controlled alternative
+  to genes_hash, as genes_hash is now formally supported for all types.
+
 ## [0.19.4] - 2025-05-05
 
 ### Added

src/chromosome/bit.rs

@@ -8,7 +8,6 @@ pub struct Bit {
     pub fitness_score: Option<FitnessValue>,
     pub genes_hash: Option<GenesHash>,
     pub age: usize,
-    pub reference_id: usize,
 }
 
 impl super::Chromosome for Bit {
@@ -40,13 +39,11 @@ impl super::Chromosome for Bit {
         self.age = 0;
         self.fitness_score = None;
         self.genes_hash = genes_hash;
-        self.reference_id = usize::MAX;
     }
     fn copy_state(&mut self, other: &Self) {
         self.age = other.age;
         self.fitness_score = other.fitness_score;
         self.genes_hash = other.genes_hash;
-        self.reference_id = other.reference_id;
     }
 }
 impl super::GenesOwner for Bit {
@@ -57,7 +54,6 @@ impl super::GenesOwner for Bit {
             fitness_score: None,
             genes_hash: None,
             age: 0,
-            reference_id: usize::MAX,
         }
     }
     fn genes(&self) -> &FixedBitSet {

src/chromosome/row.rs

@@ -7,7 +7,6 @@ pub struct Row {
     pub fitness_score: Option<FitnessValue>,
     pub genes_hash: Option<GenesHash>,
     pub age: usize,
-    pub reference_id: usize,
 }
 
 impl super::Chromosome for Row {
@@ -39,13 +38,11 @@ impl super::Chromosome for Row {
         self.age = 0;
         self.fitness_score = None;
         self.genes_hash = genes_hash;
-        self.reference_id = usize::MAX;
     }
     fn copy_state(&mut self, other: &Self) {
         self.age = other.age;
         self.fitness_score = other.fitness_score;
         self.genes_hash = other.genes_hash;
-        self.reference_id = other.reference_id;
     }
 }
 impl super::GenesPointer for Row {
@@ -55,7 +52,6 @@ impl super::GenesPointer for Row {
             fitness_score: None,
             genes_hash: None,
             age: 0,
-            reference_id: usize::MAX,
         }
     }
 }

src/chromosome/vector.rs

@@ -8,7 +8,6 @@ pub struct Vector<T: Allele> {
     pub fitness_score: Option<FitnessValue>,
     pub genes_hash: Option<GenesHash>,
     pub age: usize,
-    pub reference_id: usize,
 }
 
 impl<T: Allele> super::Chromosome for Vector<T> {
@@ -40,13 +39,11 @@ impl<T: Allele> super::Chromosome for Vector<T> {
         self.age = 0;
         self.fitness_score = None;
         self.genes_hash = genes_hash;
-        self.reference_id = usize::MAX;
     }
     fn copy_state(&mut self, other: &Self) {
         self.age = other.age;
         self.fitness_score = other.fitness_score;
         self.genes_hash = other.genes_hash;
-        self.reference_id = other.reference_id;
     }
 }
 impl<T: Allele> super::GenesOwner for Vector<T> {
@@ -57,7 +54,6 @@ impl<T: Allele> super::GenesOwner for Vector<T> {
             fitness_score: None,
             genes_hash: None,
             age: 0,
-            reference_id: usize::MAX,
         }
     }
     fn genes(&self) -> &Vec<T> {