From 53e7c4e3cac6cb661965b20f0dfd7c844ff3e922 Mon Sep 17 00:00:00 2001
From: Ahmed Gad <ahmed.f.gad@gmail.com>
Date: Wed, 23 Aug 2023 16:19:38 -0400
Subject: [PATCH] Non-Dominant Sorting for NSGA-II
---
NSGA-II/non_dominant_sorting.py | 62 +++++++++++++++++++++++++++++++++
1 file changed, 62 insertions(+)
create mode 100644 NSGA-II/non_dominant_sorting.py
diff --git a/NSGA-II/non_dominant_sorting.py b/NSGA-II/non_dominant_sorting.py
new file mode 100644
index 0000000..af677b8
--- /dev/null
+++ b/NSGA-II/non_dominant_sorting.py
@@ -0,0 +1,62 @@
+import numpy
+
+population = numpy.array([[20, 2.2],
+ [60, 4.4],
+ [65, 3.5],
+ [15, 4.4],
+ [55, 4.5],
+ [50, 1.8],
+ [80, 4.0],
+ [25, 4.6]])
+
+def non_dominant_sorting(curr_set):
+ # List of the members of the current dominant front/set.
+ dominant_set = []
+ # List of the non-members of the current dominant front/set.
+ non_dominant_set = []
+ for idx1, sol1 in enumerate(curr_set):
+ # Flag indicates whether the solution is a member of the current dominant set.
+ is_dominant = True
+ for idx2, sol2 in enumerate(curr_set):
+ if idx1 == idx2:
+ continue
+ # Zipping the 2 solutions so the corresponding genes are in the same list.
+ # The returned array is of size (N, 2) where N is the number of genes.
+ b = numpy.array(list(zip(sol1, sol2)))
+
+ #TODO Consider repacing < by > for maximization problems.
+ # Checking for if any solution dominates the current solution by applying the 2 conditions.
+ # le_eq: All elements must be True.
+ # le: Only 1 element must be True.
+ le_eq = b[:, 1] <= b[:, 0]
+ le = b[:, 1] < b[:, 0]
+
+ # If the 2 conditions hold, then a solution dominates the current solution.
+ # The current solution is not considered a member of the dominant set.
+ if le_eq.all() and le.any():
+ # print(f"{sol2} dominates {sol1}")
+ # Set the is_dominant flag to False to not insert the current solution in the current dominant set.
+ # Instead, insert it into the non-dominant set.
+ is_dominant = False
+ non_dominant_set.append(sol1)
+ break
+ else:
+ # Reaching here means the solution does not dominant the current solution.
+ # print(f"{sol2} does not dominate {sol1}")
+ pass
+
+ # If the flag is True, then no solution dominates the current solution.
+ if is_dominant:
+ dominant_set.append(sol1)
+
+ # Return the dominant and non-dominant sets.
+ return dominant_set, non_dominant_set
+
+dominant_set = []
+non_dominant_set = population.copy()
+while len(non_dominant_set) > 0:
+ d1, non_dominant_set = non_dominant_sorting(non_dominant_set)
+ dominant_set.append(d1)
+
+for i, s in enumerate(dominant_set):
+ print(f'Dominant Front Set {i+1}:\n{s}')