fix(pt_expt): centralize default-device guard in AOTInductor compilation

AOTInductor's lowering code creates tensors without explicit device=,
inheriting any active torch.set_default_device. This caused compilation
failures when tests/pt/__init__.py set a fake CUDA device. Move the
set_default_device(None) guard into _deserialize_to_file_pt2 so all
callers (tests, dp freeze, dp compress) are protected, and remove the
12 scattered workarounds from test files.

Author: Han Wang

deepmd/pt_expt/utils/serialization.py

@@ -554,8 +554,19 @@ def _deserialize_to_file_pt2(
         data, model_json_override
     )
 
-    # Compile via AOTInductor into a .pt2 package
-    aoti_compile_and_package(exported, package_path=model_file)
+    # AOTInductor's lowering code internally creates tensors (e.g.
+    # ``torch.zeros``) without an explicit ``device=`` argument.  If a
+    # non-CPU default device is active (e.g. tests/pt/__init__.py sets
+    # ``torch.set_default_device("cuda:9999999")``), the compilation fails
+    # on CPU-only builds.  Temporarily clear the default device so the
+    # inductor always targets CPU.
+    prev_device = torch.get_default_device()
+    torch.set_default_device(None)
+    try:
+        # Compile via AOTInductor into a .pt2 package
+        aoti_compile_and_package(exported, package_path=model_file)
+    finally:
+        torch.set_default_device(prev_device)
 
     # Embed metadata into the .pt2 ZIP archive
     model_def_script = data.get("model_def_script") or {}

source/tests/pt_expt/infer/test_deep_eval.py

@@ -543,13 +543,7 @@ def setUpClass(cls) -> None:
         cls.model_data = {"model": cls.model.serialize()}
         cls.tmpfile = tempfile.NamedTemporaryFile(suffix=".pt2", delete=False)
         cls.tmpfile.close()
-        # Temporarily clear default device to avoid poisoning AOTInductor
-        # compilation (tests/pt/__init__.py sets it to "cuda:9999999").
-        torch.set_default_device(None)
-        try:
-            deserialize_to_file(cls.tmpfile.name, cls.model_data)
-        finally:
-            torch.set_default_device("cuda:9999999")
+        deserialize_to_file(cls.tmpfile.name, cls.model_data)
 
         # Also save to .pte for cross-format comparison
         cls.pte_tmpfile = tempfile.NamedTemporaryFile(suffix=".pte", delete=False)
@@ -606,15 +600,11 @@ def test_get_model_def_script_with_params(self) -> None:
         with tempfile.NamedTemporaryFile(suffix=".pt2", delete=False) as f:
             tmpfile2 = f.name
         try:
-            torch.set_default_device(None)
-            try:
-                data_with_config = {
-                    **self.model_data,
-                    "model_def_script": training_config,
-                }
-                deserialize_to_file(tmpfile2, data_with_config)
-            finally:
-                torch.set_default_device("cuda:9999999")
+            data_with_config = {
+                **self.model_data,
+                "model_def_script": training_config,
+            }
+            deserialize_to_file(tmpfile2, data_with_config)
             dp2 = DeepPot(tmpfile2)
             mds = dp2.deep_eval.get_model_def_script()
             self.assertEqual(mds, training_config)
@@ -970,11 +960,7 @@ def setUpClass(cls) -> None:
         cls.model_data = {"model": cls.model.serialize()}
         cls.tmpfile = tempfile.NamedTemporaryFile(suffix=".pt2", delete=False)
         cls.tmpfile.close()
-        torch.set_default_device(None)
-        try:
-            deserialize_to_file(cls.tmpfile.name, cls.model_data)
-        finally:
-            torch.set_default_device("cuda:9999999")
+        deserialize_to_file(cls.tmpfile.name, cls.model_data)
 
         # Also save .pte for cross-format comparison
         cls.pte_tmpfile = tempfile.NamedTemporaryFile(suffix=".pte", delete=False)
@@ -1185,11 +1171,7 @@ def setUpClass(cls) -> None:
         cls.model_data = {"model": cls.model.serialize()}
         cls.tmpfile = tempfile.NamedTemporaryFile(suffix=".pt2", delete=False)
         cls.tmpfile.close()
-        torch.set_default_device(None)
-        try:
-            deserialize_to_file(cls.tmpfile.name, cls.model_data)
-        finally:
-            torch.set_default_device("cuda:9999999")
+        deserialize_to_file(cls.tmpfile.name, cls.model_data)
 
         # Also save .pte for cross-format comparison
         cls.pte_tmpfile = tempfile.NamedTemporaryFile(suffix=".pte", delete=False)

source/tests/pt_expt/infer/test_deep_eval_spin.py

@@ -154,14 +154,7 @@ def spin_model_files():
     tmpdir = tempfile.mkdtemp()
     for ext in (".pt2", ".pte"):
         path = os.path.join(tmpdir, f"spin_test{ext}")
-        # AOTInductor (.pt2) internally creates tensors using the PyTorch
-        # default device.  Clear it so compilation stays on CPU.
-        prev = torch.get_default_device()
-        torch.set_default_device(None)
-        try:
-            deserialize_to_file(path, copy.deepcopy(data))
-        finally:
-            torch.set_default_device(prev)
+        deserialize_to_file(path, copy.deepcopy(data))
         files[ext] = path
     yield files, ref_pbc, ref_nopbc
     for path in files.values():
@@ -362,12 +355,7 @@ def spin_fparam_model_files():
     tmpdir = tempfile.mkdtemp()
     for ext in (".pt2", ".pte"):
         path = os.path.join(tmpdir, f"spin_fparam_test{ext}")
-        prev = torch.get_default_device()
-        torch.set_default_device(None)
-        try:
-            deserialize_to_file(path, copy.deepcopy(data))
-        finally:
-            torch.set_default_device(prev)
+        deserialize_to_file(path, copy.deepcopy(data))
         files[ext] = path
     yield files
     for path in files.values():
@@ -426,12 +414,7 @@ def spin_aparam_model_files():
     tmpdir = tempfile.mkdtemp()
     for ext in (".pt2", ".pte"):
         path = os.path.join(tmpdir, f"spin_aparam_test{ext}")
-        prev = torch.get_default_device()
-        torch.set_default_device(None)
-        try:
-            deserialize_to_file(path, copy.deepcopy(data))
-        finally:
-            torch.set_default_device(prev)
+        deserialize_to_file(path, copy.deepcopy(data))
         files[ext] = path
     yield files
     for path in files.values():

source/tests/pt_expt/test_change_bias.py

@@ -156,14 +156,7 @@ def setUpClass(cls) -> None:
         cls.shared_pte = os.path.join(cls.tmpdir, "shared.pte")
         freeze(model=cls.model_path, output=cls.shared_pte)
         cls.shared_pt2 = os.path.join(cls.tmpdir, "shared.pt2")
-        # Clear default device: tests/pt/__init__.py may set a fake device
-        # for CPU fallback, which poisons AOTInductor compilation.
-        saved_device = torch.get_default_device()
-        torch.set_default_device(None)
-        try:
-            freeze(model=cls.model_path, output=cls.shared_pt2)
-        finally:
-            torch.set_default_device(saved_device)
+        freeze(model=cls.model_path, output=cls.shared_pt2)
 
     @classmethod
     def tearDownClass(cls) -> None: