feat: add custom __reduce__ to kernels

Author: alexfikl

sumpy/kernel.py

@@ -466,6 +466,10 @@ def __init__(self, dim: int):
             global_scaling_const=1,
         )
 
+    @override
+    def __reduce__(self) -> tuple[object, ...]:
+        return (self.__class__, (self.dim,))
+
     @property
     @override
     def is_complex_valued(self) -> bool:
@@ -496,6 +500,10 @@ def __init__(self, dim: int) -> None:
 
         super().__init__(dim, expression=expr, global_scaling_const=scaling)
 
+    @override
+    def __reduce__(self) -> tuple[object, ...]:
+        return (self.__class__, (self.dim,))
+
     @property
     @override
     def is_complex_valued(self) -> bool:
@@ -545,6 +553,10 @@ def __init__(self, dim: int) -> None:
 
         super().__init__(dim, expression=expr, global_scaling_const=scaling)
 
+    @override
+    def __reduce__(self) -> tuple[object, ...]:
+        return (self.__class__, (self.dim,))
+
     @property
     @override
     def is_complex_valued(self) -> bool:
@@ -611,6 +623,13 @@ def __init__(self,
         object.__setattr__(self, "helmholtz_k_name", helmholtz_k_name)
         object.__setattr__(self, "allow_evanescent", allow_evanescent)
 
+    @override
+    def __reduce__(self) -> tuple[object, ...]:
+        return (
+            self.__class__,
+            (self.dim, self.helmholtz_k_name, self.allow_evanescent),
+        )
+
     @property
     @override
     def is_complex_valued(self) -> bool:
@@ -698,6 +717,10 @@ def __init__(self, dim: int, yukawa_lambda_name: str = "lam") -> None:
         super().__init__(dim, expression=expr, global_scaling_const=scaling)
         object.__setattr__(self, "yukawa_lambda_name", yukawa_lambda_name)
 
+    @override
+    def __reduce__(self) -> tuple[object, ...]:
+        return (self.__class__, (self.dim, self.yukawa_lambda_name))
+
     @property
     @override
     def is_complex_valued(self) -> bool:
@@ -964,6 +987,13 @@ def __init__(self,
         object.__setattr__(self, "kcomp", kcomp)
         object.__setattr__(self, "viscosity_mu", mu)
 
+    @override
+    def __reduce__(self) -> tuple[object, ...]:
+        return (
+            self.__class__,
+            (self.dim, self.icomp, self.jcomp, self.kcomp, self.viscosity_mu),
+        )
+
     @property
     @override
     def is_complex_valued(self) -> bool:
@@ -1052,6 +1082,13 @@ def __init__(self,
         object.__setattr__(self, "viscosity_mu", mu)
         object.__setattr__(self, "poisson_ratio", nu)
 
+    @override
+    def __reduce__(self) -> tuple[object, ...]:
+        return (
+            self.__class__,
+            (self.dim, self.axis, self.viscosity_mu, self.poisson_ratio),
+        )
+
     @property
     @override
     def is_complex_valued(self) -> bool: