[Fix] Fixed version comparison to include prerelease versions (#1877)

* Fixed version comparison to include prerelease versions

Currently all tagged versions of torch 1.11.0 have version 1.11.0a0. Previously the comparison to 1.11.0 failed and self._sync_params() was still used, causing an error. This fix should include all versions of 1.11.

* Same update

Didn't realize that 1.11.0 was mentioned multiple times in the file. This fixes the other instances.

mmcv/parallel/distributed.py

@@ -45,7 +45,7 @@ class MMDistributedDataParallel(DistributedDataParallel):
                 logger='mmcv')
 
         if ('parrots' not in TORCH_VERSION
-                and digit_version(TORCH_VERSION) >= digit_version('1.11.0')):
+                and digit_version(TORCH_VERSION) >= digit_version('1.11.0a0')):
             if self._check_sync_bufs_pre_fwd():
                 self._sync_buffers()
         else:
@@ -65,7 +65,7 @@ class MMDistributedDataParallel(DistributedDataParallel):
             output = self.module.train_step(*inputs, **kwargs)
 
         if ('parrots' not in TORCH_VERSION
-                and digit_version(TORCH_VERSION) >= digit_version('1.11.0')):
+                and digit_version(TORCH_VERSION) >= digit_version('1.11.0a0')):
             if self._check_sync_bufs_post_fwd():
                 self._sync_buffers()
 
@@ -100,7 +100,7 @@ class MMDistributedDataParallel(DistributedDataParallel):
                 logger='mmcv')
 
         if ('parrots' not in TORCH_VERSION
-                and digit_version(TORCH_VERSION) >= digit_version('1.11.0')):
+                and digit_version(TORCH_VERSION) >= digit_version('1.11.0a0')):
             if self._check_sync_bufs_pre_fwd():
                 self._sync_buffers()
         else:
@@ -120,7 +120,7 @@ class MMDistributedDataParallel(DistributedDataParallel):
             output = self.module.val_step(*inputs, **kwargs)
 
         if ('parrots' not in TORCH_VERSION
-                and digit_version(TORCH_VERSION) >= digit_version('1.11.0')):
+                and digit_version(TORCH_VERSION) >= digit_version('1.11.0a0')):
             if self._check_sync_bufs_post_fwd():
                 self._sync_buffers()