Use load_async flag to not start MP iterator (#33)

bytelatent/args.py

@@ -150,11 +150,13 @@ class DataloaderArgs(BaseModel):
             enable_byte_ngrams=self.enable_byte_ngrams,
         )
         packing_iterator = PackingIterator(sampling_iterator, packing_args=packing_args)
-        mp_iterator = MultiprocessIterator(
-            packing_iterator, n_batches_to_prefetch=self.prefetch_size
-        )
-
-        return mp_iterator
+        if self.load_async:
+            mp_iterator = MultiprocessIterator(
+                packing_iterator, n_batches_to_prefetch=self.prefetch_size
+            )
+            return mp_iterator
+        else:
+            return packing_iterator
 
 
 class TrainArgs(BaseModel):