feat: support jax backend (#1671)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Added support for the "jax" backend, allowing users to work with model
files using the new `.savedmodel` suffix.
- **Bug Fixes**
- Updated error messages to include "jax" in the list of supported
backends, improving clarity for users encountering unsupported backend
issues.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Jinzhe Zeng <[email protected]>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

dpgen/generator/run.py

@@ -129,13 +129,13 @@ def _get_model_suffix(jdata) -> str:
     """Return the model suffix based on the backend."""
     mlp_engine = jdata.get("mlp_engine", "dp")
     if mlp_engine == "dp":
-        suffix_map = {"tensorflow": ".pb", "pytorch": ".pth"}
+        suffix_map = {"tensorflow": ".pb", "pytorch": ".pth", "jax": ".savedmodel"}
         backend = jdata.get("train_backend", "tensorflow")
         if backend in suffix_map:
             suffix = suffix_map[backend]
         else:
             raise ValueError(
-                f"The backend {backend} is not available. Supported backends are: 'tensorflow', 'pytorch'."
+                f"The backend {backend} is not available. Supported backends are: 'tensorflow', 'pytorch', 'jax'."
             )
         return suffix
     else:
@@ -766,6 +766,8 @@ def run_train_dp(iter_index, jdata, mdata):
     # assert train_command == "dp", "The 'train_command' should be 'dp'"     # the tests should be updated to run this command
     if suffix == ".pth":
         train_command += " --pt"
+    elif suffix == ".savedmodel":
+        train_command += " --jax"
 
     # paths
     iter_name = make_iter_name(iter_index)
@@ -803,6 +805,8 @@ def run_train_dp(iter_index, jdata, mdata):
             ckpt_suffix = ".index"
         elif suffix == ".pth":
             ckpt_suffix = ".pt"
+        elif suffix == ".savedmodel":
+            ckpt_suffix = ".jax"
         else:
             raise RuntimeError(f"Unknown suffix {suffix}")
         command = f"{{ if [ ! -f model.ckpt{ckpt_suffix} ]; then {command}{init_flag}; else {command} --restart model.ckpt; fi }}"
@@ -840,6 +844,10 @@ def run_train_dp(iter_index, jdata, mdata):
             ]
         elif suffix == ".pth":
             forward_files += [os.path.join("old", "model.ckpt.pt")]
+        elif suffix == ".savedmodel":
+            forward_files += [os.path.join("old", "model.ckpt.jax")]
+        else:
+            raise RuntimeError(f"Unknown suffix {suffix}")
     elif training_init_frozen_model is not None or training_finetune_model is not None:
         forward_files.append(os.path.join("old", f"init{suffix}"))
 
@@ -860,6 +868,10 @@ def run_train_dp(iter_index, jdata, mdata):
         ]
     elif suffix == ".pth":
         backward_files += ["model.ckpt.pt"]
+    elif suffix == ".savedmodel":
+        backward_files += ["model.ckpt.jax"]
+    else:
+        raise RuntimeError(f"Unknown suffix {suffix}")
 
     if not jdata.get("one_h5", False):
         init_data_sys_ = jdata["init_data_sys"]