optimize fake, change it to a class instead a function. test=develop

paddle/fluid/CMakeLists.txt

@@ -14,4 +14,4 @@ if(WITH_INFERENCE)
   add_subdirectory(inference)
 endif()
 
-add_subdirectory(train)
+#add_subdirectory(train)

python/paddle/reader/decorator.py

@@ -15,7 +15,7 @@
 __all__ = [
     'map_readers', 'buffered', 'compose', 'chain', 'shuffle',
     'ComposeNotAligned', 'firstn', 'xmap_readers', 'PipeReader',
-    'multiprocess_reader', 'fake'
+    'multiprocess_reader', 'Fake'
 ]
 
 from threading import Thread
@@ -506,25 +506,37 @@ class PipeReader:
                 break
 
 
-def fake(reader, data_num):
+class Fake(object):
     """
     fake reader will cache the first data it read and yield it out for data_num times.
     It is used to cache a data from real reader and use it for speed testing.
 
     :param reader: the origin reader
     :param data_num: times that this reader will yield data.
+
     :return: a fake reader.
+
+    Examples:
+        .. code-block:: python
+
+            def reader():
+                for i in range(10):
+                    yield i
+
+            fake_reader = Fake()(reader, 100)
     """
 
+    def __init__(self):
+        self.data = None
+        self.yield_num = 0
+
+    def __call__(self, reader, data_num):
         def fake_reader():
-        if fake_reader.data is None:
-            fake_reader.data = reader().next()
-        while fake_reader.yield_num < data_num:
-            yield fake_reader.data
-            fake_reader.yield_num += 1
-        fake_reader.yield_num = 0
-
-    fake_reader.data = None
-    fake_reader.yield_num = 0
+            if self.data is None:
+                self.data = reader().next()
+            while self.yield_num < data_num:
+                yield self.data
+                self.yield_num += 1
+            self.yield_num = 0
 
         return fake_reader

python/paddle/reader/tests/decorator_test.py

@@ -210,7 +210,7 @@ class TestFakeReader(unittest.TestCase):
                 yield i
 
         data_num = 100
-        fake_reader = paddle.reader.fake(reader, data_num)
+        fake_reader = paddle.reader.Fake()(reader, data_num)
         for _ in range(10):
             i = 0
             for data in fake_reader():