Fix state.to() not propagating dtype/device to constraints & expose angle_tolerance in symmetry pipeline

tests/test_constraints.py

@@ -1210,3 +1210,66 @@ def test_fix_com_system_idx_remapped_on_reordered_slice(
     c = sliced.constraints[0]
     assert isinstance(c, FixCom)
     assert sorted(c.system_idx.tolist()) == [0, 1]
+
+
+class TestConstraintToDeviceDtype:
+    """Test that state.to() propagates device/dtype to constraint tensors."""
+
+    def test_fix_atoms_dtype_propagation(
+        self, ar_supercell_sim_state: ts.SimState
+    ) -> None:
+        """FixAtoms indices should be moved to the new device by state.to()."""
+        indices = torch.tensor([0, 3, 5], dtype=torch.long)
+        ar_supercell_sim_state.constraints = [FixAtoms(atom_idx=indices)]
+        new_state = ar_supercell_sim_state.to(dtype=torch.float32)
+
+        c = new_state.constraints[0]
+        assert isinstance(c, FixAtoms)
+        assert torch.equal(c.atom_idx, indices)
+        # dtype change should not affect integer indices, but the constraint
+        # object must be a distinct copy
+        assert c is not ar_supercell_sim_state.constraints[0]
+
+    def test_fix_com_dtype_propagation(self, ar_supercell_sim_state: ts.SimState) -> None:
+        """FixCom's cached coms tensor should follow state dtype changes."""
+        ar_supercell_sim_state.constraints = [FixCom([0])]
+        # Trigger lazy COM initialisation
+        ar_supercell_sim_state.set_constrained_positions(
+            ar_supercell_sim_state.positions.clone()
+        )
+        assert ar_supercell_sim_state.constraints[0].coms is not None
+
+        new_state = ar_supercell_sim_state.to(dtype=torch.float32)
+        c = new_state.constraints[0]
+        assert isinstance(c, FixCom)
+        assert c.coms is not None
+        assert c.coms.dtype == torch.float32
+
+    @pytest.mark.parametrize("target_dtype", [torch.float32, torch.float64])
+    def test_fix_symmetry_dtype_propagation(self, target_dtype: torch.dtype) -> None:
+        """FixSymmetry rotations and reference_cells must follow dtype changes."""
+        rotations = [torch.eye(3, dtype=torch.float64).unsqueeze(0)]
+        symm_maps = [torch.zeros(1, 2, dtype=torch.long)]
+        ref_cells = [torch.eye(3, dtype=torch.float64)]
+
+        state = ts.SimState(
+            positions=torch.zeros(2, 3, dtype=torch.float64),
+            masses=torch.ones(2, dtype=torch.float64),
+            cell=torch.eye(3, dtype=torch.float64).unsqueeze(0) * 5.0,
+            pbc=True,
+            atomic_numbers=torch.tensor([14, 14]),
+            system_idx=torch.zeros(2, dtype=torch.long),
+        )
+        state.constraints = [FixSymmetry(rotations, symm_maps, reference_cells=ref_cells)]
+
+        new_state = state.to(dtype=target_dtype)
+        c = new_state.constraints[0]
+        assert isinstance(c, FixSymmetry)
+        assert c.rotations[0].dtype == target_dtype
+        assert c.reference_cells is not None
+        assert c.reference_cells[0].dtype == target_dtype
+        # integer symm_maps must stay long
+        assert c.symm_maps[0].dtype == torch.long
+        # original constraint unchanged
+        orig = state.constraints[0]
+        assert orig.rotations[0].dtype == torch.float64

torch_sim/constraints.py

@@ -151,6 +151,18 @@ def merge(cls, constraints: list[Constraint]) -> Self:
             constraints: Constraints to merge (all same type, already reindexed)
         """
 
+    @abstractmethod
+    def to(
+        self,
+        device: torch.device | None = None,
+        dtype: torch.dtype | None = None,
+    ) -> Self:
+        """Return a copy with all internal tensors moved to *device*/*dtype*.
+
+        Float tensors are cast to *dtype*; integer/bool tensors are only moved
+        to *device*.
+        """
+
 
 def _cumsum_with_zero(tensor: torch.Tensor) -> torch.Tensor:
     """Cumulative sum with a leading zero, e.g. [3, 2, 4] -> [0, 3, 5, 9]."""
@@ -272,6 +284,14 @@ def merge(cls, constraints: list[Constraint]) -> Self:
             )
         return cls(torch.cat([constraint.atom_idx for constraint in atom_constraints]))
 
+    def to(
+        self,
+        device: torch.device | None = None,
+        dtype: torch.dtype | None = None,  # noqa: ARG002
+    ) -> Self:
+        """Return a copy with atom indices moved to *device*."""
+        return type(self)(self.atom_idx.to(device=device))
+
 
 class SystemConstraint(Constraint):
     """Base class for constraints that act on specific system indices.
@@ -371,6 +391,14 @@ def merge(cls, constraints: list[Constraint]) -> Self:
             torch.cat([constraint.system_idx for constraint in system_constraints])
         )
 
+    def to(
+        self,
+        device: torch.device | None = None,
+        dtype: torch.dtype | None = None,  # noqa: ARG002
+    ) -> Self:
+        """Return a copy with system indices moved to *device*."""
+        return type(self)(self.system_idx.to(device=device))
+
 
 def merge_constraints(
     constraint_lists: list[list[Constraint]],
@@ -612,6 +640,17 @@ def __repr__(self) -> str:
         """String representation of the constraint."""
         return f"FixCom(system_idx={self.system_idx})"
 
+    def to(
+        self,
+        device: torch.device | None = None,
+        dtype: torch.dtype | None = None,
+    ) -> Self:
+        """Return a copy with tensors moved to *device*/*dtype*."""
+        new = type(self)(self.system_idx.to(device=device))
+        if self.coms is not None:
+            new.coms = self.coms.to(device=device, dtype=dtype)
+        return new
+
 
 def count_degrees_of_freedom(
     state: SimState, constraints: list[Constraint] | None = None
@@ -801,6 +840,7 @@ def from_state(
         adjust_positions: bool = True,
         adjust_cell: bool = True,
         refine_symmetry_state: bool = True,
+        angle_tolerance: float | None = None,
     ) -> Self:
         """Create from SimState, optionally refining to ideal symmetry first.
 
@@ -814,6 +854,8 @@ def from_state(
             adjust_positions: Whether to symmetrize position displacements.
             adjust_cell: Whether to symmetrize cell/stress adjustments.
             refine_symmetry_state: Whether to refine positions/cell to ideal values.
+            angle_tolerance: Angle tolerance in radians for moyopy symmetry
+                detection. If None, moyopy uses its default behaviour.
         """
         try:
             import moyopy  # noqa: F401
@@ -839,11 +881,18 @@ def from_state(
                     pos,
                     nums,
                     symprec=symprec,
+                    angle_tolerance=angle_tolerance,
                 )
                 state.cell[sys_idx] = cell.mT  # row→column vector convention
                 state.positions[start:end] = pos
             else:
-                rots, smap = prep_symmetry(cell, pos, nums, symprec=symprec)
+                rots, smap = prep_symmetry(
+                    cell,
+                    pos,
+                    nums,
+                    symprec=symprec,
+                    angle_tolerance=angle_tolerance,
+                )
 
             rotations.append(rots)
             symm_maps.append(smap)
@@ -973,6 +1022,26 @@ def reindex(self, atom_offset: int, system_offset: int) -> Self:  # noqa: ARG002
             max_cumulative_strain=self.max_cumulative_strain,
         )
 
+    def to(
+        self,
+        device: torch.device | None = None,
+        dtype: torch.dtype | None = None,
+    ) -> Self:
+        """Return a copy with tensors moved to *device*/*dtype*."""
+        return type(self)(
+            [r.to(device=device, dtype=dtype) for r in self.rotations],
+            [s.to(device=device) for s in self.symm_maps],
+            self.system_idx.to(device=device),
+            adjust_positions=self.do_adjust_positions,
+            adjust_cell=self.do_adjust_cell,
+            reference_cells=(
+                [c.to(device=device, dtype=dtype) for c in self.reference_cells]
+                if self.reference_cells is not None
+                else None
+            ),
+            max_cumulative_strain=self.max_cumulative_strain,
+        )
+
     @classmethod
     def merge(cls, constraints: list[Constraint]) -> Self:
         """Merge by concatenating rotations, symm_maps, and system indices."""

torch_sim/state.py

@@ -793,15 +793,24 @@ def _state_to_device[T: SimState](
     attrs = state.attributes
     for attr_name, attr_value in attrs.items():
         if isinstance(attr_value, torch.Tensor):
-            attrs[attr_name] = attr_value.to(device=device)
+            if attr_value.is_floating_point() and dtype is not None:
+                # also move floating point attributes like forces, velocities, etc.
+                # to dtype.
+                attrs[attr_name] = attr_value.to(device=device, dtype=dtype)
+            else:
+                # non-floating attributes like system_idx keep their dtype.
+                attrs[attr_name] = attr_value.to(device=device)
         elif isinstance(attr_value, torch.Generator):
             attrs[attr_name] = coerce_prng(attr_value, device)
 
     if dtype is not None:
-        attrs["positions"] = attrs["positions"].to(dtype=dtype)
-        attrs["masses"] = attrs["masses"].to(dtype=dtype)
-        attrs["cell"] = attrs["cell"].to(dtype=dtype)
         attrs["atomic_numbers"] = attrs["atomic_numbers"].to(dtype=torch.int)
+
+    if attrs.get("_constraints"):
+        attrs["_constraints"] = [
+            c.to(device=device, dtype=dtype) for c in attrs["_constraints"]
+        ]
+
     return type(state)(**attrs)
 
 

torch_sim/symmetrize.py

@@ -22,6 +22,7 @@ def _moyo_dataset(
     frac_pos: torch.Tensor,
     atomic_numbers: torch.Tensor,
     symprec: float = 1e-4,
+    angle_tolerance: float | None = None,
 ) -> MoyoDataset:
     """Get MoyoDataset from cell, fractional positions, and atomic numbers."""
     from moyopy import Cell, MoyoDataset
@@ -31,7 +32,7 @@ def _moyo_dataset(
         positions=frac_pos.detach().cpu().tolist(),
         numbers=atomic_numbers.detach().cpu().int().tolist(),
     )
-    return MoyoDataset(moyo_cell, symprec=symprec)
+    return MoyoDataset(moyo_cell, symprec=symprec, angle_tolerance=angle_tolerance)
 
 
 def _extract_symmetry_ops(
@@ -51,13 +52,19 @@ def _extract_symmetry_ops(
     return rotations, translations
 
 
-def get_symmetry_datasets(state: SimState, symprec: float = 1e-4) -> list[MoyoDataset]:
+def get_symmetry_datasets(
+    state: SimState,
+    symprec: float = 1e-4,
+    angle_tolerance: float | None = None,
+) -> list[MoyoDataset]:
     """Get MoyoDataset for each system in a SimState."""
     datasets = []
     for single in state.split():
         cell = single.row_vector_cell[0]
         frac = single.positions @ torch.linalg.inv(cell)
-        datasets.append(_moyo_dataset(cell, frac, single.atomic_numbers, symprec))
+        datasets.append(
+            _moyo_dataset(cell, frac, single.atomic_numbers, symprec, angle_tolerance)
+        )
     return datasets
 
 
@@ -105,14 +112,15 @@ def prep_symmetry(
     positions: torch.Tensor,
     atomic_numbers: torch.Tensor,
     symprec: float = 1e-4,
+    angle_tolerance: float | None = None,
 ) -> tuple[torch.Tensor, torch.Tensor]:
     """Get symmetry rotations and atom mappings for a structure.
 
     Returns:
         (rotations, symm_map) with shapes (n_ops, 3, 3) and (n_ops, n_atoms).
     """
     frac_pos = positions @ torch.linalg.inv(cell)
-    dataset = _moyo_dataset(cell, frac_pos, atomic_numbers, symprec)
+    dataset = _moyo_dataset(cell, frac_pos, atomic_numbers, symprec, angle_tolerance)
     rotations, translations = _extract_symmetry_ops(dataset, cell.dtype, cell.device)
     return rotations, build_symmetry_map(rotations, translations, frac_pos)
 
@@ -122,6 +130,7 @@ def _refine_symmetry_impl(
     positions: torch.Tensor,
     atomic_numbers: torch.Tensor,
     symprec: float = 0.01,
+    angle_tolerance: float | None = None,
 ) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor]:
     """Core refinement returning all intermediate data for reuse.
 
@@ -130,7 +139,7 @@ def _refine_symmetry_impl(
     """
     dtype, device = cell.dtype, cell.device
     frac_pos = positions @ torch.linalg.inv(cell)
-    dataset = _moyo_dataset(cell, frac_pos, atomic_numbers, symprec)
+    dataset = _moyo_dataset(cell, frac_pos, atomic_numbers, symprec, angle_tolerance)
     rotations, translations = _extract_symmetry_ops(dataset, dtype, device)
     n_ops, n_atoms = rotations.shape[0], positions.shape[0]
 
@@ -165,6 +174,7 @@ def refine_symmetry(
     positions: torch.Tensor,
     atomic_numbers: torch.Tensor,
     symprec: float = 0.01,
+    angle_tolerance: float | None = None,
 ) -> tuple[torch.Tensor, torch.Tensor]:
     """Symmetrize cell and positions according to the detected space group.
 
@@ -175,7 +185,7 @@ def refine_symmetry(
         (symmetrized_cell, symmetrized_positions) as row vectors.
     """
     new_cell, new_positions, _rotations, _translations = _refine_symmetry_impl(
-        cell, positions, atomic_numbers, symprec
+        cell, positions, atomic_numbers, symprec, angle_tolerance
     )
     return new_cell, new_positions
 
@@ -185,6 +195,7 @@ def refine_and_prep_symmetry(
     positions: torch.Tensor,
     atomic_numbers: torch.Tensor,
     symprec: float = 0.01,
+    angle_tolerance: float | None = None,
 ) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor]:
     """Refine symmetry and get ops/mappings in a single moyopy call.
 
@@ -195,7 +206,7 @@ def refine_and_prep_symmetry(
         (refined_cell, refined_positions, rotations, symm_map)
     """
     new_cell, new_positions, rotations, translations = _refine_symmetry_impl(
-        cell, positions, atomic_numbers, symprec
+        cell, positions, atomic_numbers, symprec, angle_tolerance
     )
     # Build symm_map on the final refined fractional coordinates
     refined_frac = new_positions @ torch.linalg.inv(new_cell)