Add InterpreterPoolExecutor support for Python 3.14+

.github/workflows/nox.yml

@@ -12,7 +12,7 @@ jobs:
       fail-fast: false
       matrix:
         platform: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: ["3.11", "3.12", "3.13"]
+        python-version: ["3.11", "3.12", "3.13", "3.14"]
 
     steps:
     - uses: actions/checkout@v4

CHANGELOG.md

@@ -1,5 +1,11 @@
 # 🗞️ Changelog
 
+## [Unreleased]
+
+**New features:**
+
+- Use `InterpreterPoolExecutor` as default executor on Python 3.14+ [\#488](https://github.com/python-adaptive/adaptive/pull/488). See also [Python documentation](https://docs.python.org/3.14/whatsnew/3.14.html#pep-734-multiple-interpreters-in-the-standard-library).
+
 ## [v1.4.0](https://github.com/python-adaptive/adaptive/tree/v1.3.0) (2025-05-13)
 
 [Full Changelog](https://github.com/python-adaptive/adaptive/compare/v1.3.2...v.1.4.0)

adaptive/_types.py

@@ -2,7 +2,8 @@
 # Workaround described in https://github.com/agronholm/typeguard/issues/456
 
 import concurrent.futures as concurrent
-from typing import TypeAlias
+import sys
+from typing import TYPE_CHECKING, TypeAlias
 
 import distributed
 import ipyparallel
@@ -11,14 +12,31 @@
 
 from adaptive.utils import SequentialExecutor
 
-ExecutorTypes: TypeAlias = (
-    concurrent.ProcessPoolExecutor
-    | concurrent.ThreadPoolExecutor
-    | SequentialExecutor
-    | loky.reusable_executor._ReusablePoolExecutor
-    | distributed.Client
-    | distributed.cfexecutor.ClientExecutor
-    | mpi4py.futures.MPIPoolExecutor
-    | ipyparallel.Client
-    | ipyparallel.client.view.ViewExecutor
-)
+# For Python 3.14+, include InterpreterPoolExecutor in the type alias
+if sys.version_info >= (3, 14):
+    if TYPE_CHECKING:
+        # Type checkers will see this when checking Python 3.14+ code
+        ExecutorTypes: TypeAlias = (
+            concurrent.ProcessPoolExecutor
+            | concurrent.ThreadPoolExecutor
+            | concurrent.InterpreterPoolExecutor  # type: ignore[attr-defined]
+            | SequentialExecutor
+            | loky.reusable_executor._ReusablePoolExecutor
+            | distributed.Client
+            | distributed.cfexecutor.ClientExecutor
+            | mpi4py.futures.MPIPoolExecutor
+            | ipyparallel.Client
+            | ipyparallel.client.view.ViewExecutor
+        )
+else:
+    ExecutorTypes: TypeAlias = (
+        concurrent.ProcessPoolExecutor
+        | concurrent.ThreadPoolExecutor
+        | SequentialExecutor
+        | loky.reusable_executor._ReusablePoolExecutor
+        | distributed.Client
+        | distributed.cfexecutor.ClientExecutor
+        | mpi4py.futures.MPIPoolExecutor
+        | ipyparallel.Client
+        | ipyparallel.client.view.ViewExecutor
+    )

adaptive/runner.py

@@ -8,6 +8,7 @@
 import itertools
 import pickle
 import platform
+import sys
 import time
 import traceback
 import warnings
@@ -44,7 +45,13 @@
 
 
 # -- Runner definitions
-if platform.system() == "Linux":
+_has_interpreter_pool = sys.version_info >= (3, 14) and hasattr(
+    concurrent, "InterpreterPoolExecutor"
+)
+
+if _has_interpreter_pool:
+    _default_executor = concurrent.InterpreterPoolExecutor  # type: ignore[misc,attr-defined]
+elif platform.system() == "Linux":
     _default_executor = concurrent.ProcessPoolExecutor  # type: ignore[misc]
 else:
     # On Windows and MacOS functions, the __main__ module must be
@@ -86,8 +93,10 @@ class BaseRunner(metaclass=abc.ABCMeta):
                `mpi4py.futures.MPIPoolExecutor`, `ipyparallel.Client` or\
                `loky.get_reusable_executor`, optional
         The executor in which to evaluate the function to be learned.
-        If not provided, a new `~concurrent.futures.ProcessPoolExecutor` on
-        Linux, and a `loky.get_reusable_executor` on MacOS and Windows.
+        If not provided, a new `~concurrent.futures.InterpreterPoolExecutor`
+        on Python 3.14+, a `~concurrent.futures.ProcessPoolExecutor` on
+        Python < 3.14 on Linux, and a `loky.get_reusable_executor` on
+        Python < 3.14 on MacOS and Windows.
     ntasks : int, optional
         The number of concurrent function evaluations. Defaults to the number
         of cores available in `executor`.
@@ -373,8 +382,10 @@ class BlockingRunner(BaseRunner):
                `mpi4py.futures.MPIPoolExecutor`, `ipyparallel.Client` or\
                `loky.get_reusable_executor`, optional
         The executor in which to evaluate the function to be learned.
-        If not provided, a new `~concurrent.futures.ProcessPoolExecutor` on
-        Linux, and a `loky.get_reusable_executor` on MacOS and Windows.
+        If not provided, a new `~concurrent.futures.InterpreterPoolExecutor`
+        on Python 3.14+, a `~concurrent.futures.ProcessPoolExecutor` on
+        Python < 3.14 on Linux, and a `loky.get_reusable_executor` on
+        Python < 3.14 on MacOS and Windows.
     ntasks : int, optional
         The number of concurrent function evaluations. Defaults to the number
         of cores available in `executor`.
@@ -520,8 +531,10 @@ class AsyncRunner(BaseRunner):
                `mpi4py.futures.MPIPoolExecutor`, `ipyparallel.Client` or\
                `loky.get_reusable_executor`, optional
         The executor in which to evaluate the function to be learned.
-        If not provided, a new `~concurrent.futures.ProcessPoolExecutor` on
-        Linux, and a `loky.get_reusable_executor` on MacOS and Windows.
+        If not provided, a new `~concurrent.futures.InterpreterPoolExecutor`
+        on Python 3.14+, a new `~concurrent.futures.ProcessPoolExecutor` on
+        Python < 3.14 on Linux, and a `loky.get_reusable_executor` on
+        Python < 3.14 on MacOS and Windows.
     ntasks : int, optional
         The number of concurrent function evaluations. Defaults to the number
         of cores available in `executor`.
@@ -1023,6 +1036,8 @@ def _get_ncores(
         import mpi4py.futures
     if with_ipyparallel and isinstance(ex, ipyparallel.client.view.ViewExecutor):
         return len(ex.view)
+    elif _has_interpreter_pool and isinstance(ex, concurrent.InterpreterPoolExecutor):  # type: ignore[attr-defined]
+        return ex._max_workers  # type: ignore[union-attr]
     elif isinstance(ex, concurrent.ProcessPoolExecutor | concurrent.ThreadPoolExecutor):
         return ex._max_workers  # type: ignore[union-attr]
     elif isinstance(ex, loky.reusable_executor._ReusablePoolExecutor):

adaptive/tests/test_runner.py

@@ -263,3 +263,26 @@ def counting_ask(self, n, tell_pending=True):
     finally:
         # Restore original method
         Learner1D.ask = original_ask
+
+
+def test_interpreter_pool_executor_detection():
+    """Test that InterpreterPoolExecutor is detected and used in Python 3.14+."""
+    import concurrent.futures as concurrent
+    import sys
+
+    from adaptive.runner import _default_executor, _has_interpreter_pool
+
+    if sys.version_info >= (3, 14) and hasattr(concurrent, "InterpreterPoolExecutor"):
+        # On Python 3.14+, InterpreterPoolExecutor should be available and used
+        assert _has_interpreter_pool is True
+        assert _default_executor == concurrent.InterpreterPoolExecutor
+    else:
+        # On older Python versions, it should not be available
+        assert _has_interpreter_pool is False
+        # Should fall back to ProcessPoolExecutor on Linux or loky on others
+        if OPERATING_SYSTEM == "Linux":
+            assert _default_executor == concurrent.ProcessPoolExecutor
+        else:
+            import loky
+
+            assert _default_executor == loky.get_reusable_executor

docs/source/tutorial/tutorial.parallelism.md

@@ -16,7 +16,13 @@ Often you will want to evaluate the function on some remote computing resources.
 
 ## `concurrent.futures`
 
-On Unix-like systems by default {class}`adaptive.Runner` creates a {class}`~concurrent.futures.ProcessPoolExecutor`, but you can also pass one explicitly e.g. to limit the number of workers:
+By default, {class}`adaptive.Runner` automatically selects the best executor based on your Python version and platform:
+
+- **Python 3.14+**: Uses {class}`~concurrent.futures.InterpreterPoolExecutor` (provides better isolation and performance)
+- **Python < 3.14 on Unix-like systems**: Uses {class}`~concurrent.futures.ProcessPoolExecutor`
+- **Python < 3.14 on Windows/macOS**: Uses `loky.get_reusable_executor` (better compatibility in interactive environments)
+
+You can also pass an executor explicitly, e.g. to limit the number of workers:
 
 ```python
 from concurrent.futures import ProcessPoolExecutor

noxfile.py

@@ -6,7 +6,7 @@
 
 nox.options.default_venv_backend = "uv"
 
-python = ["3.11", "3.12", "3.13"]
+python = ["3.11", "3.12", "3.13", "3.14"]
 num_cpus = os.cpu_count() or 1
 xdist = ("-n", "auto") if num_cpus > 2 else ()
 

pyproject.toml

@@ -16,6 +16,7 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
 ]
 dependencies = [
     "scipy",