Default max_seq_length to 128 for ExecuTorch export (#1192)

Author: swolchok

torchchat/export.py

@@ -364,13 +364,17 @@ def main(args):
         except:
             tokenizer = None
 
-        if (
-            output_dso_path is not None
-            and builder_args.max_seq_length is None
-            and not builder_args.dynamic_shapes
-        ):
-            print("Setting max_seq_length to 300 for DSO export.")
-            builder_args.max_seq_length = 300
+        if builder_args.max_seq_length is None:
+            if (
+                output_dso_path is not None
+                and not builder_args.dynamic_shapes
+            ):
+                print("Setting max_seq_length to 300 for DSO export.")
+                builder_args.max_seq_length = 300
+            elif output_pte_path is not None:
+                # The value of 128 was chosen to match the ExecuTorch Llama example setup.
+                print("Setting max_seq_length to 128 for ExecuTorch export.")
+                builder_args.max_seq_length = 128
 
         model = _initialize_model(
             builder_args,