From 0b897ea78ad479c4389da5bc4bec1b7623d4e798 Mon Sep 17 00:00:00 2001
From: eiro800 <eiro800@gmail.com>
Date: Sat, 11 Oct 2025 22:09:45 +0100
Subject: [PATCH] Fix strength calculation axis in SPEA2Survival._do to follow
 SPEA2 algorithm definition

---
 pymoo/algorithms/moo/spea2.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pymoo/algorithms/moo/spea2.py b/pymoo/algorithms/moo/spea2.py
index 71c86436a..946adf827 100644
--- a/pymoo/algorithms/moo/spea2.py
+++ b/pymoo/algorithms/moo/spea2.py
@@ -39,7 +39,7 @@ def _do(self, problem, pop, *args, n_survive=None, **kwargs):
         M = Dominator().calc_domination_matrix(F)
 
         # the number of solutions each individual dominates
-        S = (M == 1).sum(axis=0)
+        S = (M == 1).sum(axis=1)
 
         # the raw fitness of each solution - strength of its dominators
         R = ((M == -1) * S).sum(axis=1)