[Keras] ReLU6 support (#481)

nnvm/python/nnvm/frontend/keras.py

@@ -52,7 +52,7 @@ def _convert_activation(insym, keras_layer, _):
     elif act_type == 'elu':
         raise NotImplementedError('elu not implemented')
     elif act_type == 'relu6':
-        raise NotImplementedError('relu6 not implemented')
+        return _sym.clip(insym, a_min=0, a_max=6)
     elif act_type == 'softsign':
         raise NotImplementedError('softsign not implemented')
     elif act_type == 'hard_sigmoid':

nnvm/tests/python/frontend/keras/test_forward.py

@@ -116,6 +116,15 @@ def test_forward_upsample():
     verify_keras_frontend(keras_model)
 
 
+def test_forward_relu6():
+    data = keras.layers.Input(shape=(32,32,3))
+    x = keras.layers.Activation(keras.applications.mobilenet.relu6)(data)
+    x = keras.layers.Concatenate()([x, x])
+    x = keras.layers.GlobalMaxPooling2D()(x)
+    keras_model = keras.models.Model(data, x)
+    verify_keras_frontend(keras_model)
+
+
 def test_forward_vgg16():
     keras_model = keras.applications.vgg16.VGG16(include_top=True, weights=None,
         input_shape=(224,224,3), classes=1000)
@@ -142,6 +151,7 @@ if __name__ == '__main__':
     test_forward_transpose_conv()
     test_forward_separable_conv()
     test_forward_upsample()
+    test_forward_relu6()
 
     test_forward_vgg16()
     test_forward_xception()