!785 add maxpool in alexnet

Merge pull request !785 from wukesong/maxpool_alexnet

mindspore/model_zoo/alexnet.py

@@ -15,6 +15,7 @@
 """Alexnet."""
 import mindspore.nn as nn
 from mindspore.common.initializer import TruncatedNormal
+from mindspore.ops import operations as P
 
 def conv(in_channels, out_channels, kernel_size, stride=1, padding=0, pad_mode="valid"):
     weight = weight_variable()
@@ -44,7 +45,7 @@ class AlexNet(nn.Cell):
         self.conv4 = conv(384, 384, 3, pad_mode="same")
         self.conv5 = conv(384, 256, 3, pad_mode="same")
         self.relu = nn.ReLU()
-        self.max_pool2d = nn.MaxPool2d(kernel_size=3, stride=2)
+        self.max_pool2d = P.MaxPool(ksize=3, strides=2)
         self.flatten = nn.Flatten()
         self.fc1 = fc_with_initialize(6*6*256, 4096)
         self.fc2 = fc_with_initialize(4096, 4096)