fix globalbatchnorm bug

mindspore/nn/layer/normalization.py

@@ -410,7 +410,7 @@ class GlobalBatchNorm(_BatchNorm):
 
     Args:
         num_features (int): `C` from an expected input of size (N, C, H, W).
-        device_num_each_group (int): The number of devices in each group. Default: 1.
+        device_num_each_group (int): The number of devices in each group. Default: 2.
         eps (float): A value added to the denominator for numerical stability. Default: 1e-5.
         momentum (float): A floating hyperparameter of the momentum for the
             running_mean and running_var computation. Default: 0.9.
@@ -453,7 +453,7 @@ class GlobalBatchNorm(_BatchNorm):
                  moving_mean_init='zeros',
                  moving_var_init='ones',
                  use_batch_statistics=None,
-                 device_num_each_group=1):
+                 device_num_each_group=2):
         super(GlobalBatchNorm, self).__init__(num_features,
                                               eps,
                                               momentum,