Making Features as a singleton for improved caching (apache#15835)

python/mxnet/runtime.py

@@ -73,6 +73,12 @@ class Features(collections.OrderedDict):
     """
     OrderedDict of name to Feature
     """
+    instance = None
+    def __new__(cls):
+        if cls.instance is None:
+            cls.instance = super(Features, cls).__new__(cls)
+        return cls.instance
+
     def __init__(self):
         super(Features, self).__init__([(f.name, f) for f in feature_list()])
 

tests/python/unittest/test_runtime.py

@@ -21,12 +21,20 @@
 from mxnet.base import MXNetError
 from nose.tools import *
 
+
 def test_features():
     features = Features()
     print(features)
     ok_('CUDA' in features)
     ok_(len(features) >= 30)
 
+
+def test_is_singleton():
+    x = Features()
+    y = Features()
+    assert x is y
+
+
 def test_is_enabled():
     features = Features()
     for f in features:
@@ -35,6 +43,7 @@ def test_is_enabled():
         else:
             ok_(not features.is_enabled(f))
 
+
 @raises(RuntimeError)
 def test_is_enabled_not_existing():
     features = Features()