introducing @register_dynamic decorator to solve dynamic-reuse issue

PySDM/builder.py

@@ -121,8 +121,8 @@ def build(
             self._resolve_attribute(attr_name)
         self.req_attr_names = None
 
-        for dynamic in self.particulator.dynamics.values():
-            dynamic.register(self)
+        for key, dynamic in self.particulator.dynamics.items():
+            self.particulator.dynamics[key] = dynamic.instantiate(builder=self)
 
         single_buffer_for_all_products = np.empty(self.particulator.mesh.grid)
         for product in products:

PySDM/dynamics/ambient_thermodynamics.py

@@ -2,7 +2,10 @@
 environment-sync triggering class
 """
 
+from PySDM.dynamics.impl import register_dynamic
 
+
+@register_dynamic()
 class AmbientThermodynamics:
     def __init__(self):
         self.particulator = None

PySDM/dynamics/aqueous_chemistry.py

@@ -13,12 +13,14 @@
     M,
     SpecificGravities,
 )
+from PySDM.dynamics.impl import register_dynamic
 
 DEFAULTS = namedtuple("_", ("pH_min", "pH_max", "pH_rtol", "ionic_strength_threshold"))(
     pH_min=-1.0, pH_max=14.0, pH_rtol=1e-6, ionic_strength_threshold=0.02 * M
 )
 
 
+@register_dynamic()
 class AqueousChemistry:  # pylint: disable=too-many-instance-attributes
     def __init__(
         self,

PySDM/dynamics/collisions/collision.py

@@ -23,6 +23,7 @@
     RandomGeneratorOptimizerNoPair,
 )
 from PySDM.physics import si
+from PySDM.dynamics.impl import register_dynamic
 
 # pylint: disable=too-many-lines
 
@@ -36,6 +37,7 @@
 )
 
 
+@register_dynamic()
 class Collision:  # pylint: disable=too-many-instance-attributes
     def __init__(
         self,
@@ -288,6 +290,7 @@ def compute_gamma(self, prob, rand, is_first_in_pair, out):
         )
 
 
+@register_dynamic()
 class Coalescence(Collision):
     def __init__(
         self,
@@ -316,6 +319,7 @@ def __init__(
         )
 
 
+@register_dynamic()
 class Breakup(Collision):
     def __init__(
         self,

PySDM/dynamics/condensation.py

@@ -7,7 +7,8 @@
 
 import numpy as np
 
-from ..physics import si
+from PySDM.physics import si
+from PySDM.dynamics.impl import register_dynamic
 
 DEFAULTS = namedtuple("_", ("rtol_x", "rtol_thd", "cond_range", "schedule"))(
     rtol_x=1e-6,
@@ -17,6 +18,7 @@
 )
 
 
+@register_dynamic()
 class Condensation:  # pylint: disable=too-many-instance-attributes
     def __init__(
         self,

PySDM/dynamics/displacement.py

@@ -11,9 +11,12 @@
 
 import numpy as np
 
+from PySDM.dynamics.impl import register_dynamic
+
 DEFAULTS = namedtuple("_", ("rtol", "adaptive"))(rtol=1e-2, adaptive=True)
 
 
+@register_dynamic()
 class Displacement:  # pylint: disable=too-many-instance-attributes
     def __init__(
         self,

PySDM/dynamics/eulerian_advection.py

@@ -2,7 +2,10 @@
 wrapper class for triggering integration in the Eulerian advection solver
 """
 
+from PySDM.dynamics.impl import register_dynamic
 
+
+@register_dynamic()
 class EulerianAdvection:
     def __init__(self, solvers):
         self.solvers = solvers

PySDM/dynamics/freezing.py

@@ -7,8 +7,10 @@
     TimeDependentAttributes,
 )
 from PySDM.physics.heterogeneous_ice_nucleation_rate import Null
+from PySDM.dynamics.impl import register_dynamic
 
 
+@register_dynamic()
 class Freezing:
     def __init__(self, *, singular=True, record_freezing_temperature=False, thaw=False):
         assert not (record_freezing_temperature and singular)

PySDM/dynamics/impl/__init__.py

@@ -1 +1,3 @@
 """ stuff not intended to be imported from user code """
+
+from .register_dynamic import register_dynamic

PySDM/dynamics/impl/register_dynamic.py

@@ -0,0 +1,21 @@
+""" decorator for dynamics classes
+ensuring that their instances can be re-used with multiple builders """
+
+from copy import deepcopy
+
+
+def _instantiate(self, *, builder):
+    copy = deepcopy(self)
+    copy.register(builder=builder)
+    return copy
+
+
+def register_dynamic():
+    def decorator(cls):
+        if hasattr(cls, "instantiate"):
+            assert cls.instantiate is _instantiate
+        else:
+            setattr(cls, "instantiate", _instantiate)
+        return cls
+
+    return decorator

PySDM/dynamics/isotopic_fractionation.py

@@ -4,11 +4,13 @@
 """
 
 from PySDM.dynamics.condensation import Condensation
+from PySDM.dynamics.impl import register_dynamic
 
 LIGHT_ISOTOPES = ("1H", "16O")
 HEAVY_ISOTOPES = ("2H", "3H", "17O", "18O")
 
 
+@register_dynamic()
 class IsotopicFractionation:
     def __init__(self, isotopes: tuple = HEAVY_ISOTOPES):
         self.isotopes = isotopes

PySDM/dynamics/relaxed_velocity.py

@@ -6,8 +6,10 @@
 
 from PySDM.attributes.impl.attribute import Attribute
 from PySDM.particulator import Particulator
+from PySDM.dynamics.impl import register_dynamic
 
 
+@register_dynamic()
 class RelaxedVelocity:  # pylint: disable=too-many-instance-attributes
     """
     A dynamic which updates the fall momentum according to a relaxation timescale

tests/unit_tests/dynamics/test_impl_register_dynamic.py

@@ -0,0 +1,39 @@
+""" checks if @register_product makes dynamics instances reusable """
+
+import numpy as np
+
+from PySDM import Builder
+from PySDM.backends import CPU
+from PySDM.environments import Box
+from PySDM.dynamics.impl import register_dynamic
+
+
+def test_impl_register_dynamic():
+    # arrange
+    @register_dynamic()
+    class Dynamic:
+        def __init__(self):
+            self.particulator = None
+
+        def register(self, *, builder: Builder):
+            self.particulator = builder.particulator
+
+    dynamic = Dynamic()
+    kwargs = {"n_sd": 0, "backend": CPU(), "environment": Box(dt=0, dv=0)}
+    builders = [Builder(**kwargs), Builder(**kwargs)]
+
+    # act
+    for builder in builders:
+        builder.add_dynamic(dynamic)
+        builder.build(
+            attributes={"multiplicity": np.empty(0), "water mass": np.empty(0)}
+        )
+
+    # assert
+    assert dynamic.particulator is None
+    assert builders[0].particulator is not builders[1].particulator
+    for builder in builders:
+        assert (
+            builder.particulator.dynamics["Dynamic"].particulator
+            is builder.particulator
+        )