fix __len__

basedformer/dataset.py

@@ -68,7 +68,7 @@ class ShardedImageDataset(data.Dataset):
         self.executor = concurrent.futures.ThreadPoolExecutor(max_workers=self.threads)
 
     def __len__(self):
-        return len(self.metadata) // (self.bsz * self.world_size)
+        return len(self.metadata) // self.bsz
     
     def __getitem__(self, key):
         key = self.skip + key