diff --git a/ge/alias.py b/ge/alias.py
index a1eb094..b8a7592 100644
--- a/ge/alias.py
+++ b/ge/alias.py
@@ -10,9 +10,8 @@ def create_alias_table(area_ratio):
     l = len(area_ratio)
     accept, alias = [0] * l, [0] * l
     small, large = [], []
-    area_ratio_ = np.array(area_ratio) * l
-    for i, prob in enumerate(area_ratio_):
-        if prob < 1.0:
+    for i, prob in enumerate(area_ratio):
+        if prob*l < 1.0:
             small.append(i)
         else:
             large.append(i)