fix tournament return duplicate fittest

Took 42 minutes

tests/test_utils.py

@@ -320,11 +320,13 @@ def test_tournament(supply_population):
     assert parents.len() == 2
     assert supply_population.contains(parents[0]) == True
     assert supply_population.contains(parents[1]) == True
+    assert parents[0] != parents[1]
 
     parents = F.tournament(supply_population, 0.0)  # force to use random parents not fittest ('else' condition)
     assert parents.len() == 2
     assert supply_population.contains(parents[0]) == True
     assert supply_population.contains(parents[1]) == True
+    assert parents[0] != parents[1]
 
 
 def test_routes_ending_indices_attr(supply_depot: Depot):

utils/functional.py

@@ -122,6 +122,7 @@ def tournament(population: Population, tournament_probability: float = 0.8, size
     3. Select another random unique sample from the population
     4. Find fittest chromosomes from each sampled populations and return them as new population.
     5. Randomly choose two chromosomes and return them as a new population.
+
     :param population: An instance of `Population` class
     :param tournament_probability: The probability of using fittest or random sample (=0.8)
     :param size: The size of population to be sampled. By default, we use Binary tournament (size = 2).
@@ -133,6 +134,8 @@ def tournament(population: Population, tournament_probability: float = 0.8, size
         second_sample = extract_population(population, size)
         first_fittest = fittest_chromosome(first_sample)
         second_fittest = fittest_chromosome(second_sample)
+        while first_sample == second_fittest:
+            second_fittest = fittest_chromosome(second_sample)
         return Population(0, [first_fittest, second_fittest])
     else:
         indices = random.sample(range(0, first_sample.len()), 2)