update SyncBatchNorm API for primitive implementation to support apex.parallel.convert_syncbn_model

apex/parallel/optimized_sync_batchnorm.py

@@ -55,7 +55,7 @@ class SyncBatchNorm(_BatchNorm):
         >>> inp = torch.randn(10, 14, 14, 100).cuda()
     """
 
-    def __init__(self, num_features, eps=1e-5, momentum=0.1, affine=True, track_running_stats=True, process_group=None, channel_last = False):
+    def __init__(self, num_features, eps=1e-5, momentum=0.1, affine=True, track_running_stats=True, process_group=None, channel_last=False):
         super(SyncBatchNorm, self).__init__(num_features, eps=eps, momentum=momentum, affine=affine, track_running_stats=track_running_stats)
         self.process_group = process_group
         self.channel_last = channel_last

apex/parallel/sync_batchnorm.py

@@ -48,7 +48,9 @@ class SyncBatchNorm(_BatchNorm):
 
     warned = False
 
-    def __init__(self, num_features, eps=1e-5, momentum=0.1, affine=True, track_running_stats=True, process_group=None):
+    def __init__(self, num_features, eps=1e-5, momentum=0.1, affine=True, track_running_stats=True, process_group=None, channel_last=False):
+        if channel_last == True:
+            raise AttributeError("channel_last is not supported by primitive SyncBatchNorm implementation. Try install apex with `--cuda_ext` if channel_last is desired.")
 
         if not SyncBatchNorm.warned:
             print("Warning:  using Python fallback for SyncBatchNorm, possibly because apex was installed without --cuda_ext.  The exception raised when attempting to import the cuda backend was: ", self.syncbn_import_error)