use threadpool as executor

src/okipy/strategies.py

@@ -1,6 +1,6 @@
 from dataclasses import dataclass
+from multiprocessing.pool import ThreadPool
 from typing import Callable, TypeVar
-from multiprocessing import Pool
 
 
 T = TypeVar("T")
@@ -17,7 +17,7 @@ class RunStrategy:
 class Parallel(RunStrategy):
     procs: None | int = None
     def run_all(self, items: list[T], oper: Callable[[T], O]) -> list[O]:
-        return Pool(self.procs).map(oper, items)
+        return ThreadPool(self.procs).map(oper, items)
 
 
 class Sequential(RunStrategy):