fix windows hang (#627)

ppgan/engine/trainer.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import os
+import sys
 import time
 import copy
 
@@ -35,6 +36,7 @@ class IterLoader:
         self._dataloader = dataloader
         self.iter_loader = iter(self._dataloader)
         self._epoch = 1
+        self._inner_iter = 0
 
     @property
     def epoch(self):
@@ -42,12 +44,17 @@ class IterLoader:
 
     def __next__(self):
         try:
+            if sys.platform == "Windows" and self._inner_iter == len(
+                    self._dataloader) - 1:
+                self._inner_iter = 0
+                raise StopIteration
             data = next(self.iter_loader)
         except StopIteration:
             self._epoch += 1
             self.iter_loader = iter(self._dataloader)
             data = next(self.iter_loader)
 
+        self._inner_iter += 1
         return data
 
     def __len__(self):