Add OpenMM <7.6 backwards compatability (#401)

openff/evaluator/datasets/curation/components/conversion.py

@@ -59,7 +59,11 @@ class ConvertExcessDensityData(CurationComponent):
     def _molecular_weight(cls, smiles):
 
         from openff.toolkit.topology import Molecule
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         molecule = Molecule.from_smiles(smiles, allow_undefined_stereo=True)
 

openff/evaluator/datasets/curation/components/filtering.py

@@ -686,7 +686,11 @@ def _apply(
     ) -> pandas.DataFrame:
 
         from openff.toolkit.topology import Molecule
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         def filter_function(data_row):
 

openff/evaluator/datasets/taproom/taproom.py

@@ -189,7 +189,11 @@ def _build_substance(
             The built substance.
         """
         from openff.toolkit.topology import Molecule
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         substance = Substance()
 

openff/evaluator/datasets/thermoml/thermoml.py

@@ -846,7 +846,11 @@ def _smiles_to_molecular_weight(smiles):
         """
 
         from openff.toolkit.topology import Molecule
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         try:
 

openff/evaluator/forcefield/system.py

@@ -7,7 +7,11 @@
 if TYPE_CHECKING:
 
     from openff.toolkit.topology import Topology
-    from openmm import System
+
+    try:
+        from openmm import System
+    except ImportError:
+        from simtk.openmm import System
 
 
 class ParameterizedSystem(TypedBaseModel):
@@ -31,7 +35,11 @@ def topology_path(self) -> str:
     def topology(self) -> "Topology":
 
         from openff.toolkit.topology import Molecule, Topology
-        from openmm import app
+
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
 
         pdb_file = app.PDBFile(self._topology_path)
 
@@ -51,7 +59,10 @@ def system_path(self) -> str:
 
     @property
     def system(self) -> "System":
-        import openmm
+        try:
+            import openmm
+        except ImportError:
+            from simtk import openmm
 
         with open(self._system_path) as file:
             system = openmm.XmlSerializer.deserialize(file.read())

openff/evaluator/protocols/analysis.py

@@ -34,7 +34,11 @@
 )
 
 if typing.TYPE_CHECKING:
-    import openmm
+
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
 
 
 E0 = 8.854187817e-12 * unit.farad / unit.meter  # Taken from QCElemental
@@ -578,8 +582,12 @@ def _extract_charges(
             The charge on each atom in the system if any are present, otherwise
             none.
         """
-        import openmm
-        from openmm import unit as openmm_unit
+        try:
+            import openmm
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk import openmm
+            from simtk.openmm import unit as openmm_unit
 
         forces = [
             system.getForce(force_index)

openff/evaluator/protocols/coordinates.py

@@ -7,7 +7,11 @@
 from os import path
 
 import numpy as np
-from openmm import app
+
+try:
+    from openmm import app
+except ImportError:
+    from simtk.openmm import app
 
 from openff.evaluator import unit
 from openff.evaluator.attributes import UNDEFINED
@@ -446,7 +450,11 @@ def _execute(self, directory, available_resources):
 
         import mdtraj
         from openeye import oechem, oedocking
-        from openmm import unit as openmm_unit
+
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         if (
             len(self.ligand_substance.components) != 1

openff/evaluator/protocols/forcefield.py

@@ -12,9 +12,17 @@
 from enum import Enum
 
 import numpy as np
-import openmm
+
+try:
+    import openmm
+except ImportError:
+    from simtk import openmm
 import requests
-from openmm import app
+
+try:
+    from openmm import app
+except ImportError:
+    from simtk.openmm import app
 
 from openff.evaluator.attributes import UNDEFINED
 from openff.evaluator.forcefield import (
@@ -547,7 +555,10 @@ def _built_template(molecule, force_field_source):
         openmm.app.ForceField
             The force field template.
         """
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         initial_request_url = force_field_source.request_url
         empty_stream = io.BytesIO(b"\r\n")
@@ -643,7 +654,10 @@ def _parameterize_molecule(self, molecule, force_field_source, cutoff):
         openmm.System
             The parameterized system.
         """
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         template = self._built_template(molecule, force_field_source)
 
@@ -682,7 +696,10 @@ def _apply_opls_mixing_rules(system):
         system: openmm.System
             The system object to apply the OPLS mixing rules to.
         """
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         forces = [system.getForce(index) for index in range(system.getNumForces())]
         forces = [force for force in forces if isinstance(force, openmm.NonbondedForce)]
@@ -825,7 +842,10 @@ def _run_tleap(molecule, force_field_source, directory):
         str
             The file path to the `rst7` file.
         """
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         # Change into the working directory.
         with temporarily_change_directory(directory):

openff/evaluator/protocols/gradients.py

@@ -52,7 +52,10 @@ class ZeroGradients(Protocol, abc.ABC):
 
     def _execute(self, directory, available_resources):
 
-        from openmm import unit as openmm_unit
+        try:
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk.openmm import unit as openmm_unit
 
         force_field_source = ForceFieldSource.from_json(self.force_field_path)
 

openff/evaluator/protocols/openmm.py

@@ -45,7 +45,11 @@
 
 if TYPE_CHECKING:
 
-    import openmm
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
+
     from mdtraj import Trajectory
     from openff.toolkit.topology import Topology
     from openff.toolkit.typing.engines.smirnoff import ForceField
@@ -84,8 +88,12 @@ def _evaluate_energies(
     -------
         The array containing the evaluated potentials.
     """
-    import openmm
-    from openmm import unit as openmm_unit
+    try:
+        import openmm
+        from openmm import unit as openmm_unit
+    except ImportError:
+        from simtk import openmm
+        from simtk.openmm import unit as openmm_unit
 
     integrator = openmm.VerletIntegrator(0.1 * openmm_unit.femtoseconds)
 
@@ -178,7 +186,10 @@ def _compute_gradients(
         The amount to perturb for the force field parameter by.
     """
 
-    import openmm
+    try:
+        import openmm
+    except ImportError:
+        from simtk import openmm
 
     gradients = defaultdict(list)
     observables.clear_gradients()
@@ -334,9 +345,14 @@ class OpenMMEnergyMinimisation(BaseEnergyMinimisation):
 
     def _execute(self, directory, available_resources):
 
-        import openmm
-        from openmm import app
-        from openmm import unit as openmm_unit
+        try:
+            import openmm
+            from openmm import app
+            from openmm import unit as openmm_unit
+        except ImportError:
+            from simtk import openmm
+            from simtk.openmm import app
+            from simtk.openmm import unit as openmm_unit
 
         platform = setup_platform_with_resources(available_resources)
 
@@ -445,7 +461,10 @@ def __init__(self, file, append=False):
 
         def report(self, simulation, state):
 
-            from openmm import app
+            try:
+                from openmm import app
+            except ImportError:
+                from simtk.openmm import app
 
             if self._dcd is None:
 
@@ -486,7 +505,11 @@ def __init__(self, protocol_id):
     def _execute(self, directory, available_resources):
 
         import mdtraj
-        from openmm import app
+
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
 
         # We handle most things in OMM units here.
         temperature = self.thermodynamic_state.temperature
@@ -596,9 +619,14 @@ def _setup_simulation_objects(self, temperature, pressure, available_resources):
             the simulation.
         """
 
-        import openmm
         import openmmtools
-        from openmm import app
+
+        try:
+            import openmm
+            from openmm import app
+        except ImportError:
+            from simtk import openmm
+            from simtk.openmm import app
 
         # Create a platform with the correct resources.
         if not self.allow_gpu_platforms:
@@ -678,7 +706,10 @@ def _write_checkpoint_file(self, current_step_number, context):
         context: openmm.Context
             The current OpenMM context.
         """
-        import openmm
+        try:
+            import openmm
+        except ImportError:
+            from simtk import openmm
 
         # Write the current state to disk
         state = context.getState(
@@ -831,7 +862,10 @@ def _resume_from_checkpoint(self, context):
         int
             The current step number.
         """
-        import openmm
+        try:
+            import openmm
+        except ImportError:
+            from simtk import openmm
 
         current_step_number = 0
 
@@ -953,7 +987,10 @@ def _simulate(self, context, integrator):
         integrator: openmm.Integrator
             The integrator to evolve the simulation with.
         """
-        from openmm import app
+        try:
+            from openmm import app
+        except ImportError:
+            from simtk.openmm import app
 
         # Define how many steps should be taken.
         total_number_of_steps = (