Update non_dominated_sorting.py (#653)

* Update non_dominated_sorting.py

Fixing error #611

* Update non_dominated_sorting.py

pymoo/util/nds/non_dominated_sorting.py

@@ -1,5 +1,5 @@
 import numpy as np
-
+import sys
 from pymoo.util.dominator import Dominator
 from pymoo.util.function_loader import load_function
 
@@ -53,7 +53,7 @@ def do(self, F, return_rank=False, only_non_dominated_front=False, n_stop_if_ran
 
 def rank_from_fronts(fronts, n):
     # create the rank array and set values
-    rank = np.full(n, 1e16, dtype=int)
+    rank = np.full(n, sys.maxsize, dtype=int)
     for i, front in enumerate(fronts):
         rank[front] = i