fix bug in locallyshuffledata initialization

tensorpack/dataflow/common.py

@@ -332,8 +332,8 @@ class LocallyShuffleData(ProxyDataFlow, RNGDataFlow):
             dp = next(self.ds_itr)
             for _ in range(self.nr_reuse):
                 self.q.append(dp)
-        for _ in range(self.q.maxlen - len(self.q)):
         try:
+            while self.q.maxlen > len(self.q):
                 add_next()
         except StopIteration:
             logger.error("LocallyShuffleData: cache_size is larger than the size of ds!")