enforce popsize in increments of 4

Author: eirikurj

pyoptsparse/pyNSGA2/pyNSGA2.py

@@ -34,6 +34,9 @@ def __init__(self, raiseError=True, options={}):
         if isinstance(nsga2, str) and raiseError:
             raise ImportError(nsga2)
 
+        if self.getOption("PopSize") % 4 != 0:
+            raise ValueError("Option 'PopSize' must be a multiple of 4")
+
     @staticmethod
     def _getInforms():
         informs = {}

pyoptsparse/pyNSGA2/source/tourselect.c

@@ -32,7 +32,7 @@ void selection (population *old_pop, population *new_pop, Global global, int *nr
         a2[rand] = a2[i];
         a2[i] = temp;
     }
-    for (i=0; i<global.popsize-4; i+=4)
+    for (i=0; i<global.popsize; i+=4)
     {
         parent1 = tournament (&old_pop->ind[a1[i]], &old_pop->ind[a1[i+1]], global);
         parent2 = tournament (&old_pop->ind[a1[i+2]], &old_pop->ind[a1[i+3]], global);

tests/test_nsga2_multi_objective.py

@@ -73,6 +73,13 @@ def test_opt(self, n_obj):
             assert_allclose(sol.fStar["obj1"], 12.0, atol=tol, rtol=tol)
             assert_allclose(sol.fStar["obj2"], 0.0, atol=tol, rtol=tol)
 
+    def test_options(self):
+        with self.assertRaises(ValueError):
+            # PopSize must be a multiple of 4
+            self.setup_optProb(1)
+            optOptions = {"PopSize": 5}
+            sol = self.optimize(optOptions=optOptions)
+
 
 if __name__ == "__main__":
     unittest.main()