threadpoolctl
threadpoolctl
Decision gist · record as of 2026-08-14
Yes. This is a lightweight, actively maintained utility for anyone using thread-pool-backed libraries in parallel workloads. It has no dependencies, a permissive license, no known vulnerabilities, and solves a real performance problem in nested parallelism scenarios.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Low friction installation with no runtime dependencies.
- Active maintenance with recent releases and a stable repository.
License · maintenance · safety
BSD-3-Clause (permissive) — BSD-3-Clause is permissive; you may use, modify, and distribute this package freely in commercial and private projects.
last release 2025-03-13 (519 days) · last repo commit 2026-08-11 · 431 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 204,185,238 downloads/mo, #201 on PyPI
Alternatives
Verify before relying
pip install threadpoolctl
from threadpoolctl import threadpool_limits
with threadpool_limits(limits=1, user_api='blas'):
# BLAS calls limited to one thread- Whether all BLAS implementations (MKL, OpenBLAS, FlexiBLAS) are equally well supported across platforms.
- Performance overhead of introspection and limit-setting operations in tight loops.
- Compatibility with thread-pool libraries loaded after package import.
What it is and what it does
threadpoolctl provides Python helpers to inspect and limit the number of threads used by native thread-pool libraries (BLAS, OpenMP) that are loaded by scientific computing packages. It solves the problem of thread oversubscription—when nested parallelism causes more threads to be spawned than CPU cores, degrading performance. The package offers both a command-line interface to query loaded thread-pools and a Python API with context managers and decorators to temporarily cap thread counts in specific code sections.
It supports multiple BLAS backends and OpenMP implementations, and can be used either functionally via `threadpool_limits()` or through an object-oriented `ThreadpoolController` for more fine-grained control. The library has no runtime dependencies and supports Python 3.9 and later.
Use it for
- Prevent thread oversubscription when calling BLAS operations inside already-parallelized code.
- Query which thread-pool libraries are loaded by imported packages for debugging performance issues.
- Dynamically switch BLAS backends at runtime using FlexiBLAS without restarting.
- Decorate functions to enforce single-threaded BLAS calls while keeping outer-loop parallelism.
- Manage thread counts in distributed pipelines with nested parallelism.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
This is a lightweight, actively maintained utility for anyone using thread-pool-backed libraries in parallel workloads. It has no dependencies, a permissive license, no known vulnerabilities, and solves a real performance problem in nested parallelism scenarios.
Install
threadpoolctl on PyPI
Before you install
Low friction installation with no runtime dependencies. Active maintenance with recent releases and a stable repository.
License in practice
BSD-3-Clause is permissive; you may use, modify, and distribute this package freely in commercial and private projects.
Quickstart
pip install threadpoolctl
from threadpoolctl import threadpool_limits
with threadpool_limits(limits=1, user_api='blas'):
# BLAS calls limited to one threadVerify before relying
- Whether all BLAS implementations (MKL, OpenBLAS, FlexiBLAS) are equally well supported across platforms.
- Performance overhead of introspection and limit-setting operations in tight loops.
- Compatibility with thread-pool libraries loaded after package import.
Package facts
| License | BSD-3-Clause permissive |
| Python support | Supports the current Python release >=3.9 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 519 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 204,185,238 / month, #201 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Intended Audience :: DevelopersLicense :: OSI Approved :: BSD LicenseProgramming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.9Topic :: Software Development :: Libraries :: Python Modules |
Evidence: threadpoolctl-3.6.0-py3-none-any.whl
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See also tcmlib · intel-openmp · onemkl-sycl-blas · onemkl-sycl-lapack · mkl-include · onemkl-sycl-sparse · onemkl-sycl-rng · mkl · onemkl-sycl-dft · onemkl-license