[medicalseg]Fix syncbn (#3109)

* fix_single_card_syncbn_convert

Author: shiyutang

contrib/MedicalSeg/medicalseg/cvlibs/config.py

@@ -21,7 +21,7 @@
 import yaml
 
 from medicalseg.cvlibs import manager
-from medicalseg.utils import logger
+from medicalseg.utils import logger, get_sys_env
 
 # todo: check and edit the unnecessary components
 
@@ -318,9 +318,13 @@ def model(self) -> paddle.nn.Layer:
 
         if not self._model:
             self._model = self._load_object(model_cfg)
-        if paddle.get_device() != 'cpu':
+
+        env_info = get_sys_env()
+        if paddle.get_device() == 'gpu' and env_info['Paddle compiled with cuda'] \
+            and env_info['GPUs used'] and paddle.distributed.ParallelEnv().nranks > 1:
             self._model = paddle.nn.SyncBatchNorm.convert_sync_batchnorm(
                 self._model)
+            logger.info("Convert bn to sync_bn")
 
         return self._model