Features/constraints

CHANGELOG.md

@@ -1,6 +1,16 @@
 <!-- markdownlint-disable -->
 # Changelog
 
+## Unreleased
+
+### 🎉 New Features
+* Constraints support for molecular dynamics and optimization by @thomasloux in [#294](https://github.com/TorchSim/torch-sim/pull/294)
+  - Added `FixAtoms` constraint to fix specific atoms in place
+  - Added `FixCom` constraint to prevent center of mass drift
+  - Constraints automatically adjust degrees of freedom for accurate temperature calculations
+  - Full support across all integrators (NVE, NVT, NPT) and optimizers (FIRE, Gradient Descent)
+  - Constraints preserved during state manipulation (slicing, splitting, concatenation)
+
 ## v0.4.0
 
 Thank you to everyone who contributed to this release! This release includes significant API improvements and breaking changes. @janosh led a major API redesign to improve usability. @stefanbringuier added heat flux calculations. @curtischong continued improving type safety across the codebase. @CompRhys, @orionarcher, @WillEngler, and @thomasloux all made valuable contributions. 🚀

examples/scripts/3_Dynamics/3.10_Hybrid_swap_mc.py

@@ -67,9 +67,8 @@ class HybridSwapMCState(ts.SwapMCState, MDState):
         last_swap: Last swap attempted
     """
 
-    last_permutation: torch.Tensor
     _atom_attributes = (
-        ts.SwapMCState._atom_attributes | MDState._atom_attributes | {"last_permutation"}  # noqa: SLF001
+        ts.SwapMCState._atom_attributes | MDState._atom_attributes  # noqa: SLF001
     )
     _system_attributes = (
         ts.SwapMCState._system_attributes | MDState._system_attributes  # noqa: SLF001

examples/tutorials/hybrid_swap_tutorial.py

@@ -100,9 +100,11 @@ class HybridSwapMCState(SwapMCState, MDState):
     from MDState.
     """
 
-    last_permutation: torch.Tensor
     _atom_attributes = (
-        MDState._atom_attributes | {"last_permutation"}  # noqa: SLF001
+        ts.SwapMCState._atom_attributes | MDState._atom_attributes  # noqa: SLF001
+    )
+    _system_attributes = (
+        ts.SwapMCState._system_attributes | MDState._system_attributes  # noqa: SLF001
     )