MobileNetV2 (apache#9614)

* MobileNetV2

* add mobilenetv2 to gluon vision model zoo.

* code reformat use autopep8 and isort.
fix pylint style check error.
add docstring, disable some check.
delete duplicate code in example.

* change ver to version.

* use exist helper.

* model code refactor.

* fix line too long.

* remove invalid name option.

* merge output operations.

* change variables name

* fix line too long.

* s -> stride

* add output name_scope

* remove relu in first conv2d.

* change block name from BottleNeck to LinearBottleneck.

* resolve conflict

* fix parameter name.

* correct strides

* add mobilenetv2 to unittest.

* use autopep8 to reformat code.

* add mobilenetv2 symbols to gluon.vision

* add relu in 1st conv2d.

* code refactor by using helpers.

* split mobilenet v1 and v2 apis.

CONTRIBUTORS.md

@@ -156,3 +156,4 @@ List of Contributors
 * [Meghna Baijal](https://github.com/mbaijal)
 * [Tao Hu](https://github.com/dongzhuoyao)
 * [Sorokin Evgeniy](https://github.com/TheTweak)
+* [dwSun](https://github.com/dwSun/)

example/image-classification/symbols/mobilenetv2.py

@@ -0,0 +1,76 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+
+# -*- coding:utf-8 -*-
+'''
+MobileNetV2, implemented in Gluon.
+
+Reference:
+Inverted Residuals and Linear Bottlenecks:
+Mobile Networks for Classification, Detection and Segmentation
+https://arxiv.org/abs/1801.04381
+'''
+__author__ = 'dwSun'
+__date__ = '18/1/31'
+
+import mxnet as mx
+
+from mxnet.gluon.model_zoo.vision.mobilenet import MobileNetV2
+
+
+__all__ = ['MobileNetV2', 'get_symbol']
+
+
+def get_symbol(num_classes=1000, multiplier=1.0, ctx=mx.cpu(), **kwargs):
+    r"""MobileNetV2 model from the
+    `"Inverted Residuals and Linear Bottlenecks:
+      Mobile Networks for  Classification, Detection and Segmentation"
+    <https://arxiv.org/abs/1801.04381>`_ paper.
+
+    Parameters
+    ----------
+    num_classes : int, default 1000
+        Number of classes for the output layer.
+    multiplier : float, default 1.0
+        The width multiplier for controling the model size. The actual number of channels
+        is equal to the original channel size multiplied by this multiplier.
+    ctx : Context, default CPU
+        The context in which to initialize the model weights.
+    """
+    net = MobileNetV2(multiplier=multiplier, classes=num_classes, **kwargs)
+    net.initialize(ctx=ctx, init=mx.init.Xavier())
+    net.hybridize()
+
+    data = mx.sym.var('data')
+    out = net(data)
+    sym = mx.sym.SoftmaxOutput(out, name='softmax')
+    return sym
+
+
+def plot_net():
+    """
+    Visualize the network.
+    """
+    sym = get_symbol(1000, prefix='mob_')
+
+    # plot network graph
+    mx.viz.plot_network(sym, shape={'data': (8, 3, 224, 224)},
+                        node_attrs={'shape': 'oval', 'fixedsize': 'fasl==false'}).view()
+
+
+if __name__ == '__main__':
+    plot_net()

python/mxnet/gluon/model_zoo/vision/__init__.py

@@ -28,6 +28,7 @@
 -  `SqueezeNet`_
 -  `VGG`_
 -  `MobileNet`_
+-  `MobileNetV2`_
 
 You can construct a model with random weights by calling its constructor:
 
@@ -69,6 +70,7 @@
 .. _SqueezeNet: https://arxiv.org/abs/1602.07360
 .. _VGG: https://arxiv.org/abs/1409.1556
 .. _MobileNet: https://arxiv.org/abs/1704.04861
+.. _MobileNetV2: https://arxiv.org/abs/1801.04381
 """
 
 from .alexnet import *
@@ -85,6 +87,7 @@
 
 from .mobilenet import *
 
+
 def get_model(name, **kwargs):
     """Returns a pre-defined model by name
 
@@ -135,11 +138,15 @@ def get_model(name, **kwargs):
               'mobilenet1.0': mobilenet1_0,
               'mobilenet0.75': mobilenet0_75,
               'mobilenet0.5': mobilenet0_5,
-              'mobilenet0.25': mobilenet0_25
+              'mobilenet0.25': mobilenet0_25,
+              'mobilenetv2_1.0': mobilenet_v2_1_0,
+              'mobilenetv2_0.75': mobilenet_v2_0_75,
+              'mobilenetv2_0.5': mobilenet_v2_0_5,
+              'mobilenetv2_0.25': mobilenet_v2_0_25
              }
     name = name.lower()
     if name not in models:
         raise ValueError(
-            'Model %s is not supported. Available options are\n\t%s'%(
+            'Model %s is not supported. Available options are\n\t%s' % (
                 name, '\n\t'.join(sorted(models.keys()))))
     return models[name](**kwargs)