fix(pt_expt): move optimize_ddp into _compile_model, resolve test symlinks

Move torch._dynamo.config.optimize_ddp = False from module level into
_compile_model() so it only applies when compile is active. Resolve
symlinks in test_fitting_stat.py data paths for reliable CI access.

Author: Han Wang

deepmd/pt_expt/train/training.py

@@ -24,14 +24,6 @@
 import torch
 import torch.distributed as dist
 
-# Disable DDPOptimizer: our compile region wraps only the inner compute
-# function, not the whole DDP model.  DDPOptimizer assumes it owns the
-# full model graph and splits at bucket boundaries, producing subgraphs
-# whose outputs include symbolic integers.  AOT Autograd then crashes
-# with ``'int' object has no attribute 'meta'``
-# (pytorch/pytorch#134182).
-torch._dynamo.config.optimize_ddp = False
-
 from deepmd.dpmodel.common import (
     to_numpy_array,
 )
@@ -903,6 +895,14 @@ def _compile_model(self, compile_opts: dict[str, Any]) -> None:
         needed.  The coord extension + nlist build (data-dependent
         control flow) are kept outside the compiled region.
         """
+        # Disable DDPOptimizer: our compile region wraps only the inner
+        # compute function, not the whole DDP model.  DDPOptimizer assumes
+        # it owns the full model graph and splits at bucket boundaries,
+        # producing subgraphs whose outputs include symbolic integers.
+        # AOT Autograd then crashes with ``'int' object has no attribute
+        # 'meta'`` (pytorch/pytorch#134182).
+        torch._dynamo.config.optimize_ddp = False
+
         from deepmd.dpmodel.utils.nlist import (
             build_neighbor_list,
             extend_coord_with_ghosts,

source/tests/pt_expt/fitting/test_fitting_stat.py

@@ -117,13 +117,18 @@ def _get_weighted_fitting_stat(
     return weighted_avg, weighted_std
 
 
-# Paths to the water data used by PT tests
-_PT_DATA = str(Path(__file__).parent.parent.parent / "pt" / "water" / "data" / "data_0")
+# Paths to the water data used by PT tests.
+# resolve() follows the ``pt/water -> model/water`` symlink so numpy can
+# always open the real file, even on CI runners where symlink handling
+# can be fragile.
+_PT_DATA = str(
+    (Path(__file__).parent.parent.parent / "pt" / "water" / "data" / "data_0").resolve()
+)
 _PT_DATA_NO_FPARAM = str(
-    Path(__file__).parent.parent.parent / "pt" / "water" / "data" / "data_1"
+    (Path(__file__).parent.parent.parent / "pt" / "water" / "data" / "data_1").resolve()
 )
 _PT_DATA_SINGLE = str(
-    Path(__file__).parent.parent.parent / "pt" / "water" / "data" / "single"
+    (Path(__file__).parent.parent.parent / "pt" / "water" / "data" / "single").resolve()
 )
 
 _descriptor_se_e2_a = {