support tf.layers in argscope (#778)

* support tf.layers in argscope

* rename

* "lib"->"module"; add docs

* typo

examples/basics/mnist-tflayers.py

@@ -20,6 +20,7 @@ from tensorpack.tfutils import summary, get_current_tower_context
 from tensorpack.dataflow import dataset
 
 IMAGE_SIZE = 28
+enable_argscope_for_module(tf.layers)
 
 
 class Model(ModelDesc):
@@ -38,12 +39,13 @@ class Model(ModelDesc):
 
         image = image * 2 - 1   # center the pixels values at zero
 
-        l = tf.layers.conv2d(image, 32, 3, padding='same', activation=tf.nn.relu, name='conv0')
+        with argscope([tf.layers.conv2d], padding='same', activation=tf.nn.relu):
+            l = tf.layers.conv2d(image, 32, 3, name='conv0')
             l = tf.layers.max_pooling2d(l, 2, 2, padding='valid')
-        l = tf.layers.conv2d(l, 32, 3, padding='same', activation=tf.nn.relu, name='conv1')
-        l = tf.layers.conv2d(l, 32, 3, padding='same', activation=tf.nn.relu, name='conv2')
+            l = tf.layers.conv2d(l, 32, 3, name='conv1')
+            l = tf.layers.conv2d(l, 32, 3, name='conv2')
             l = tf.layers.max_pooling2d(l, 2, 2, padding='valid')
-        l = tf.layers.conv2d(l, 32, 3, padding='same', activation=tf.nn.relu, name='conv3')
+            l = tf.layers.conv2d(l, 32, 3, name='conv3')
             l = tf.layers.flatten(l)
             l = tf.layers.dense(l, 512, activation=tf.nn.relu, name='fc0')
             l = tf.layers.dropout(l, rate=0.5,
@@ -60,7 +62,7 @@ class Model(ModelDesc):
         accuracy = tf.reduce_mean(correct, name='accuracy')
 
         # This will monitor training error (in a moving_average fashion):
-        # 1. write the value to tensosrboard
+        # 1. write the value to tensorboard
         # 2. write the value to stat.json
         # 3. print the value after each epoch
         train_error = tf.reduce_mean(1 - correct, name='train_error')

tensorpack/tfutils/argscope.py

@@ -4,8 +4,10 @@
 from contextlib import contextmanager
 from collections import defaultdict
 import copy
+from functools import wraps
+from inspect import isfunction, getmembers
 
-__all__ = ['argscope', 'get_arg_scope']
+__all__ = ['argscope', 'get_arg_scope', 'enable_argscope_for_module']
 
 _ArgScopeStack = []
 
@@ -60,3 +62,28 @@ def get_arg_scope():
         return _ArgScopeStack[-1]
     else:
         return defaultdict(dict)
+
+
+def argscope_mapper(func):
+    """Decorator for function to support argscope
+    """
+    @wraps(func)
+    def wrapped_func(*args, **kwargs):
+        actual_args = copy.copy(get_arg_scope()[func.__name__])
+        actual_args.update(kwargs)
+        out_tensor = func(*args, **actual_args)
+        return out_tensor
+    # argscope requires this property
+    wrapped_func.symbolic_function = None
+    return wrapped_func
+
+
+def enable_argscope_for_module(module):
+    """
+    Overwrite all functions of a given module to support argscope.
+    Note that this function monkey-patches the module and therefore could have unexpected consequences.
+    It has been only tested to work well with `tf.layers` module.
+    """
+    for name, obj in getmembers(module):
+        if isfunction(obj):
+            setattr(module, name, argscope_mapper(obj))