fix: pickle compatible implementation of downsamplers (#44)

* 🔥 first pickle compatible implementation of downsamplers

* 🖊️ review code

* 🙈 fix linting issue

---------

Co-authored-by: jvdd <boebievdd@gmail.com>

tests/test_tsdownsample.py

@@ -38,7 +38,7 @@ def generate_all_downsamplers() -> Iterable[AbstractDownsampler]:
 
 
 @pytest.mark.parametrize("downsampler", generate_all_downsamplers())
-def test_serialization(downsampler: AbstractDownsampler):
+def test_serialization_copy(downsampler: AbstractDownsampler):
     """Test serialization."""
     from copy import copy, deepcopy
 
@@ -53,6 +53,19 @@ def test_serialization(downsampler: AbstractDownsampler):
     assert np.all(orig_downsampled == ddc_downsampled)
 
 
+@pytest.mark.parametrize("downsampler", generate_all_downsamplers())
+def test_serialization_pickle(downsampler: AbstractDownsampler):
+    """Test serialization."""
+    import pickle
+
+    dc = pickle.loads(pickle.dumps(downsampler))
+
+    arr = np.arange(10_000)
+    orig_downsampled = downsampler.downsample(arr, n_out=100)
+    dc_downsampled = dc.downsample(arr, n_out=100)
+    assert np.all(orig_downsampled == dc_downsampled)
+
+
 @pytest.mark.parametrize("downsampler", generate_rust_downsamplers())
 def test_rust_downsampler(downsampler: AbstractDownsampler):
     """Test the Rust downsamplers."""

tsdownsample/downsamplers.py

@@ -10,8 +10,9 @@
 
 
 class MinMaxDownsampler(AbstractRustDownsampler):
-    def __init__(self) -> None:
-        super().__init__(_tsdownsample_rs.minmax)
+    @property
+    def rust_mod(self):
+        return _tsdownsample_rs.minmax
 
     @staticmethod
     def _check_valid_n_out(n_out: int):
@@ -21,8 +22,9 @@ def _check_valid_n_out(n_out: int):
 
 
 class M4Downsampler(AbstractRustDownsampler):
-    def __init__(self):
-        super().__init__(_tsdownsample_rs.m4)
+    @property
+    def rust_mod(self):
+        return _tsdownsample_rs.m4
 
     @staticmethod
     def _check_valid_n_out(n_out: int):
@@ -32,13 +34,15 @@ def _check_valid_n_out(n_out: int):
 
 
 class LTTBDownsampler(AbstractRustDownsampler):
-    def __init__(self):
-        super().__init__(_tsdownsample_rs.lttb)
+    @property
+    def rust_mod(self):
+        return _tsdownsample_rs.lttb
 
 
 class MinMaxLTTBDownsampler(AbstractRustDownsampler):
-    def __init__(self):
-        super().__init__(_tsdownsample_rs.minmaxlttb)
+    @property
+    def rust_mod(self):
+        return _tsdownsample_rs.minmaxlttb
 
     def downsample(
         self, *args, n_out: int, minmax_ratio: int = 30, parallel: bool = False, **_

tsdownsample/downsampling_interface.py

@@ -143,24 +143,47 @@ def downsample(self, *args, n_out: int, **kwargs):  # x and y are optional
 class AbstractRustDownsampler(AbstractDownsampler, ABC):
     """RustDownsampler interface-class, subclassed by concrete downsamplers."""
 
-    def __init__(self, resampling_mod: ModuleType):
+    def __init__(self):
         super().__init__(_rust_dtypes, _y_rust_dtypes)  # same for x and y
-        self.rust_mod = resampling_mod
 
-        # Store the single core sub module
-        self.mod_single_core = self.rust_mod.scalar
+    @property
+    def rust_mod(self) -> ModuleType:
+        """The compiled Rust module for the current downsampler."""
+        raise NotImplementedError
+
+    @property
+    def mod_single_core(self) -> ModuleType:
+        """Get the single-core Rust module.
+
+        Returns
+        -------
+        ModuleType
+            If SIMD compiled module is available, that one is returned. Otherwise, the
+            scalar compiled module is returned.
+        """
         if hasattr(self.rust_mod, "simd"):
             # use SIMD implementation if available
-            self.mod_single_core = self.rust_mod.simd
+            return self.rust_mod.simd
+        return self.rust_mod.scalar
+
+    @property
+    def mod_multi_core(self) -> Union[ModuleType, None]:
+        """Get the multi-core Rust module.
 
-        # Store the multi-core sub module (if present)
-        self.mod_multi_core = None  # no multi-core implementation (default)
+        Returns
+        -------
+        ModuleType or None
+            If SIMD parallel compiled module is available, that one is returned.
+            Otherwise, the scalar parallel compiled module is returned.
+            If no parallel compiled module is available, None is returned.
+        """
         if hasattr(self.rust_mod, "simd_parallel"):
             # use SIMD implementation if available
-            self.mod_multi_core = self.rust_mod.simd_parallel
+            return self.rust_mod.simd_parallel
         elif hasattr(self.rust_mod, "scalar_parallel"):
             # use scalar implementation if available (when no SIMD available)
-            self.mod_multi_core = self.rust_mod.scalar_parallel
+            return self.rust_mod.scalar_parallel
+        return None  # no parallel compiled module available
 
     @staticmethod
     def _switch_mod_with_y(