create buffered data reader decorator and tests

python/CMakeLists.txt

@@ -24,6 +24,7 @@ add_custom_target(paddle_python ALL DEPENDS
     ${OUTPUT_DIR}/.timestamp)
 
 add_subdirectory(paddle/trainer_config_helpers/tests)
+add_subdirectory(paddle/reader/tests)
 
 install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/dist/
     DESTINATION opt/paddle/share/wheels

python/paddle/reader/__init__.py

@@ -0,0 +1,15 @@
+# Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from decorator import *

python/paddle/reader/decorator.py

@@ -0,0 +1,60 @@
+# Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+__all__ = ['buffered']
+
+from Queue import Queue
+from threading import Thread
+
+
+def buffered(reader, size):
+    """Creates a buffered data reader.
+
+    The buffered data reader will read and save data entries into a buffer.
+    Reading from the buffered data reader will proceed as long as the buffer
+    is not empty.
+    
+    Args:
+        reader: the data reader to read from.
+        size: max buffer size.
+    
+    Returns:
+        The buffered data reader.
+    """
+
+    class EndSignal():
+        pass
+
+    end = EndSignal()
+
+    def read_worker(r, q):
+        for d in r:
+            q.put(d)
+        q.put(end)
+
+    def create_reader():
+        r = reader()
+        q = Queue(maxsize=size)
+        t = Thread(
+            target=read_worker, args=(
+                r,
+                q, ))
+        t.daemon = True
+        t.start()
+        e = q.get()
+        while e != end:
+            yield e
+            e = q.get()
+
+    return create_reader

python/paddle/reader/tests/CMakeLists.txt

@@ -0,0 +1,4 @@
+add_test(NAME reader_decorator_test
+  COMMAND ${PROJ_ROOT}/paddle/.set_python_path.sh -d ${PROJ_ROOT}/python/
+        ${PYTHON_EXECUTABLE} ${PROJ_ROOT}/python/paddle/reader/decorator_test.py
+    WORKING_DIRECTORY ${PROJ_ROOT}/python/paddle)

python/paddle/reader/tests/decorator_test.py

@@ -0,0 +1,50 @@
+# Copyright PaddlePaddle contributors. All Rights Reserved
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import unittest
+import paddle.reader
+import time
+
+
+def reader_10(dur):
+    for i in range(10):
+        time.sleep(dur)
+        yield i
+
+
+class TestBuffered(unittest.TestCase):
+    def test_read(self):
+        for size in range(20):
+            b = paddle.reader.buffered(lambda: reader_10(0), size)
+            c = 0
+            for i in b():
+                self.assertEqual(i, c)
+                c += 1
+            self.assertEqual(c, 10)
+
+    def test_buffering(self):
+        # read have 30ms delay.
+        b = paddle.reader.buffered(lambda: reader_10(0.03), 10)
+        last_time = time.time()
+        for idx, i in enumerate(b()):
+            elapsed_time = time.time() - last_time
+            if i == 0:
+                time.sleep(0.3)
+            else:
+                # read time should be short, meaning already buffered.
+                self.assertLess(elapsed_time, 0.01)
+            last_time = time.time()
+
+
+if __name__ == '__main__':
+    unittest.main()