Replace _face_distance with more efficient calculation (ageitgey#19)

JKCooper2 · ageitgey · commit 99641c5052a9 · 2017-03-19T13:20:27.000-07:00
From http://stackoverflow.com/questions/7741878/how-to-apply-numpy-linalg-norm-to-each-row-of-a-matrix Running time comparisons (prev vs. new, performed using faces = np.random.rand(n, 128), face_to_compare = np.random.rand(1, 128)) n = 1M: 5.3s vs. 1.1s n = 5M: 26.9s vs. 6.6s n = 10M: 52.6s vs. 23s
diff --git a/face_recognition/api.py b/face_recognition/api.py
@@ -61,7 +61,7 @@ def _face_distance(faces, face_to_compare):
     :param face_to_compare: A face encoding to compare against
     :return: A list with the distance for each face in the same order as the 'faces' array
     """
-    return np.array([np.linalg.norm(face - face_to_compare) for face in faces])
+    return np.linalg.norm(faces - face_to_compare, axis=1)
 
 
 def load_image_file(filename, mode='RGB'):
