
Andy Faff contributed to the scipy/scipy and numpy/numpy repositories, delivering robust improvements to optimization workflows, CI/CD pipelines, and numerical APIs. Over 18 months, Andy engineered scalable parallelization for optimization routines, enhanced random number generation APIs, and modernized build systems using Python, YAML, and shell scripting. His work included refactoring core algorithms for maintainability, implementing deterministic testing for reliability, and streamlining cross-platform CI for faster feedback and security. By clarifying documentation and strengthening configuration management, Andy reduced regression risk and improved developer experience. The depth of his contributions reflects strong expertise in scientific computing, DevOps, and software engineering.
April 2026 monthly summary focusing on CI improvements and cross-repo reliability. Delivered consolidated Windows ARM64 CI workflow optimizations in numpy and scipy, improving build reliability, reducing setup complexity, and accelerating feedback loops for contributors. Key work included dependency handling, environment setup, and platform detection refinements.
April 2026 monthly summary focusing on CI improvements and cross-repo reliability. Delivered consolidated Windows ARM64 CI workflow optimizations in numpy and scipy, improving build reliability, reducing setup complexity, and accelerating feedback loops for contributors. Key work included dependency handling, environment setup, and platform detection refinements.
March 2026 focused on stabilizing and accelerating SciPy’s CI and release workflows, with targeted maintenance to reduce drift and improve cross-platform consistency. Key improvements include a revamped CI pipeline for faster PR validation, cross-platform wheel synchronization with scipy-release, and a tightened maintenance workflow to reduce config drift. The month also delivered essential documentation updates to support maintainers and users, and several reliability fixes to Windows/macOS/Linux build processes.
March 2026 focused on stabilizing and accelerating SciPy’s CI and release workflows, with targeted maintenance to reduce drift and improve cross-platform consistency. Key improvements include a revamped CI pipeline for faster PR validation, cross-platform wheel synchronization with scipy-release, and a tightened maintenance workflow to reduce config drift. The month also delivered essential documentation updates to support maintainers and users, and several reliability fixes to Windows/macOS/Linux build processes.
February 2026 — SciPy/scipy: Deterministic seeding for Differential Evolution tests implemented to ensure reproducible test outcomes, improving CI reliability and debugging efficiency. The change reduces flaky test failures and supports more trustworthy release validation. Key commit: 4f5274d7422d3ba928f94d3b87201f791f27f97b (#24549).
February 2026 — SciPy/scipy: Deterministic seeding for Differential Evolution tests implemented to ensure reproducible test outcomes, improving CI reliability and debugging efficiency. The change reduces flaky test failures and supports more trustworthy release validation. Key commit: 4f5274d7422d3ba928f94d3b87201f791f27f97b (#24549).
January 2026 monthly summary for scipy/scipy development focusing on constraint documentation improvements. Delivered targeted documentation clarifications for the keep_feasible parameter in NonlinearConstraint and LinearConstraint classes, enabling users to understand feasibility maintenance at the end of iterations and its behavior in infeasible regions. This aligns with documentation quality goals and reduces potential misuse in optimization workflows. No major code changes were made this month beyond documentation updates.
January 2026 monthly summary for scipy/scipy development focusing on constraint documentation improvements. Delivered targeted documentation clarifications for the keep_feasible parameter in NonlinearConstraint and LinearConstraint classes, enabling users to understand feasibility maintenance at the end of iterations and its behavior in infeasible regions. This aligns with documentation quality goals and reduces potential misuse in optimization workflows. No major code changes were made this month beyond documentation updates.
December 2025 performance summary for scipy/scipy. Focused on modernizing the codebase for upcoming stack changes, cleaning up deprecated features, and strengthening test coverage to improve reliability across Python/Numpy versions and platforms.
December 2025 performance summary for scipy/scipy. Focused on modernizing the codebase for upcoming stack changes, cleaning up deprecated features, and strengthening test coverage to improve reliability across Python/Numpy versions and platforms.
Month: 2025-11 performance summary for numpy/numpy and scipy/scipy. Focused on delivering business value through reliability, security, and scalable performance improvements. Key features delivered: - numpy/numpy: CI/CD modernization by migrating from Azure Pipelines to GitHub Actions, removing Windows jobs, and strengthening build validation and security for code fetch. Added Python header inclusion validation to ensure correct compilation order for Python 3.11 on 32-bit Linux, resulting in faster, more secure, and more reliable builds. Major bugs fixed: - scipy/scipy: Memory management and reference cycle resilience in DifferentialEvolutionSolver by removing reference cycles and improving mutation handling; added tests to detect ref cycles to ensure proper deallocation. - scipy/scipy: Robust multiprocessing handling in ScalarFunction and Hessian evaluation, fixing refcycles that could lead to excessive open files and ensuring ScalarHessWrapper does not hold unnecessary pool references, improving multi-threaded optimization stability. Overall impact and accomplishments: - Improved CI reliability and security across numpy, leading to faster feedback cycles and fewer disruptions from build issues. - Enhanced memory safety and resource management in SciPy, increasing robustness of long-running optimization workflows and reducing risk of memory leaks and file descriptor exhaustion. - Strengthened cross-repo collaboration patterns and test coverage to catch regressions earlier. Technologies/skills demonstrated: - GitHub Actions, CI/CD modernization, security scanning, Python header validation, cross-repo coordination, memory management, multiprocessing, test-driven development, and performance-oriented debugging.
Month: 2025-11 performance summary for numpy/numpy and scipy/scipy. Focused on delivering business value through reliability, security, and scalable performance improvements. Key features delivered: - numpy/numpy: CI/CD modernization by migrating from Azure Pipelines to GitHub Actions, removing Windows jobs, and strengthening build validation and security for code fetch. Added Python header inclusion validation to ensure correct compilation order for Python 3.11 on 32-bit Linux, resulting in faster, more secure, and more reliable builds. Major bugs fixed: - scipy/scipy: Memory management and reference cycle resilience in DifferentialEvolutionSolver by removing reference cycles and improving mutation handling; added tests to detect ref cycles to ensure proper deallocation. - scipy/scipy: Robust multiprocessing handling in ScalarFunction and Hessian evaluation, fixing refcycles that could lead to excessive open files and ensuring ScalarHessWrapper does not hold unnecessary pool references, improving multi-threaded optimization stability. Overall impact and accomplishments: - Improved CI reliability and security across numpy, leading to faster feedback cycles and fewer disruptions from build issues. - Enhanced memory safety and resource management in SciPy, increasing robustness of long-running optimization workflows and reducing risk of memory leaks and file descriptor exhaustion. - Strengthened cross-repo collaboration patterns and test coverage to catch regressions earlier. Technologies/skills demonstrated: - GitHub Actions, CI/CD modernization, security scanning, Python header validation, cross-repo coordination, memory management, multiprocessing, test-driven development, and performance-oriented debugging.
October 2025 Monthly Summary — SciPy and NumPy CI/test improvements focused on macOS 15 Intel environments, stabilizing Accelerate tests, and advancing cross-repo build reliability. Delivered targeted CI enhancements that reduce flaky tests, speed up feedback, and improve cross-platform performance verification, enabling faster releases with higher confidence in numerical correctness.
October 2025 Monthly Summary — SciPy and NumPy CI/test improvements focused on macOS 15 Intel environments, stabilizing Accelerate tests, and advancing cross-repo build reliability. Delivered targeted CI enhancements that reduce flaky tests, speed up feedback, and improve cross-platform performance verification, enabling faster releases with higher confidence in numerical correctness.
During September 2025, I delivered key enhancements to SciPy's optimization API and upgraded the CI/testing environment, delivering tangible improvements in experimentation flexibility, debugging efficiency, and release readiness. The changes target both the optimization workflow and the stability of the pre-release pipeline, aligning with business goals of faster feature validation and more reliable software releases.
During September 2025, I delivered key enhancements to SciPy's optimization API and upgraded the CI/testing environment, delivering tangible improvements in experimentation flexibility, debugging efficiency, and release readiness. The changes target both the optimization workflow and the stability of the pre-release pipeline, aligning with business goals of faster feature validation and more reliable software releases.
Month 2025-08: Delivered targeted CI workflow optimization for Pyodide testing in the numpy/numpy repository. Removed wheel upload steps and scheduling overhead to accelerate feedback, reduce CI resource usage, and improve reliability. Implemented via a focused change set that narrows CI to Pyodide tests.
Month 2025-08: Delivered targeted CI workflow optimization for Pyodide testing in the numpy/numpy repository. Removed wheel upload steps and scheduling overhead to accelerate feedback, reduce CI resource usage, and improve reliability. Implemented via a focused change set that narrows CI to Pyodide tests.
Monthly work summary for 2025-07 in the scipy/scipy repo focused on documentation accuracy for least_squares x_scale with the lm method. Delivered a documentation correction to reflect that x_scale is described as 'jac', aligning guidance with intended behavior. No API changes or code-level alterations were introduced in this period.
Monthly work summary for 2025-07 in the scipy/scipy repo focused on documentation accuracy for least_squares x_scale with the lm method. Delivered a documentation correction to reflect that x_scale is described as 'jac', aligning guidance with intended behavior. No API changes or code-level alterations were introduced in this period.
June 2025: Focused on stabilizing the Shgo complex cache path in SciPy, delivering a targeted fix to the split_edge caching mechanism. The change improves reliability and performance of the optimization process under complex cache scenarios, reducing edge-case failures and stabilizing results.
June 2025: Focused on stabilizing the Shgo complex cache path in SciPy, delivering a targeted fix to the split_edge caching mechanism. The change improves reliability and performance of the optimization process under complex cache scenarios, reducing edge-case failures and stabilizing results.
May 2025 (2025-05) monthly summary for scipy/scipy. Highlights include reliable wheel downloads, clearer API expectations for optimization results, and strengthened CI security. Key deliverables: a bug fix to the wheel downloader URL handling to ensure PyPI simple index is used for wheel fetch, including renaming and using appropriate staging URL constants; documentation improvements clarifying behavior of minimize and its interaction with missing attributes on OptimizeResult; and CI security hardening and logging improvements to tighten permissions and improve logging posture. These changes reduce user-facing failures, improve developer experience, and bolster security in the CI pipeline. Impact focus: - Reliability: Stable wheel retrieval reduces install/CI failures. - Clarity: Users and developers understand OptimizeResult attributes and minimize callback behavior. - Security: Hardened CI and better logging provide faster detection and response. Technologies/skills demonstrated: - Python tooling, packaging scripts, Build/CI configuration, security hardening, API documentation, and code maintenance.
May 2025 (2025-05) monthly summary for scipy/scipy. Highlights include reliable wheel downloads, clearer API expectations for optimization results, and strengthened CI security. Key deliverables: a bug fix to the wheel downloader URL handling to ensure PyPI simple index is used for wheel fetch, including renaming and using appropriate staging URL constants; documentation improvements clarifying behavior of minimize and its interaction with missing attributes on OptimizeResult; and CI security hardening and logging improvements to tighten permissions and improve logging posture. These changes reduce user-facing failures, improve developer experience, and bolster security in the CI pipeline. Impact focus: - Reliability: Stable wheel retrieval reduces install/CI failures. - Clarity: Users and developers understand OptimizeResult attributes and minimize callback behavior. - Security: Hardened CI and better logging provide faster detection and response. Technologies/skills demonstrated: - Python tooling, packaging scripts, Build/CI configuration, security hardening, API documentation, and code maintenance.
April 2025 monthly summary for scipy/scipy: focused on robustness, testing coverage, and API behavior changes. Implemented a VectorFunction refactor to improve state integrity; expanded CI to cover array API compatibility; and updated Least Squares default x_scale handling with associated docs/tests. These changes reduce downstream side effects, improve cross-API compatibility, and clarify default behavior for users and developers. Result: more reliable numerical routines, better developer experience, and stronger alignment with SciPy's API expectations.
April 2025 monthly summary for scipy/scipy: focused on robustness, testing coverage, and API behavior changes. Implemented a VectorFunction refactor to improve state integrity; expanded CI to cover array API compatibility; and updated Least Squares default x_scale handling with associated docs/tests. These changes reduce downstream side effects, improve cross-API compatibility, and clarify default behavior for users and developers. Result: more reliable numerical routines, better developer experience, and stronger alignment with SciPy's API expectations.
March 2025: Focused on CI/documentation improvements for the QEMU binfmt workflow in numpy/numpy and Cirrus CI simplification for macOS wheel uploads. Delivered clearer developer guidance, streamlined CI config, and improved maintainability, contributing to faster feedback cycles and more reliable builds.
March 2025: Focused on CI/documentation improvements for the QEMU binfmt workflow in numpy/numpy and Cirrus CI simplification for macOS wheel uploads. Delivered clearer developer guidance, streamlined CI config, and improved maintainability, contributing to faster feedback cycles and more reliable builds.
February 2025: Delivered scalable parallel worker support across SciPy optimization workflows, delivering tangible business value through faster solves and improved resource utilization. Key accomplishments include enabling workers in Newton-CG, CG, and TNC (with fixed-variable callbacks), adding workers keyword support for trust-krylov and trust-ncg, and introducing worker-based parallelization in least_squares. Documentation and tutorials were expanded to cover worker usage in optimizers, updated docstrings, and vectorization notes; VectorFunction groundwork was laid with initial work and sensible defaults for ScalarFunction and VectorFunction to simplify usage. Code quality improved via lint updates, test maintenance (including moving equal-bounds callback tests) and wrapper class renames. A notable bug fix prevented unintended behavior by not applying FD options for Hessian VectorFunction. Overall, these efforts boost performance, clarity, and maintainability, establishing a strong foundation for future VectorFunction enhancements and broader solver parallelization.
February 2025: Delivered scalable parallel worker support across SciPy optimization workflows, delivering tangible business value through faster solves and improved resource utilization. Key accomplishments include enabling workers in Newton-CG, CG, and TNC (with fixed-variable callbacks), adding workers keyword support for trust-krylov and trust-ncg, and introducing worker-based parallelization in least_squares. Documentation and tutorials were expanded to cover worker usage in optimizers, updated docstrings, and vectorization notes; VectorFunction groundwork was laid with initial work and sensible defaults for ScalarFunction and VectorFunction to simplify usage. Code quality improved via lint updates, test maintenance (including moving equal-bounds callback tests) and wrapper class renames. A notable bug fix prevented unintended behavior by not applying FD options for Hessian VectorFunction. Overall, these efforts boost performance, clarity, and maintainability, establishing a strong foundation for future VectorFunction enhancements and broader solver parallelization.
February 2025-01: SciPy optimization improvements focused on reliability, parity, and maintainability. Delivered standardized callback handling and result interpretation across multiple optimizers (dogbox, least_squares, trf), and strengthened the least_squares test suite to improve coverage, readability, and performance. These changes reduce regression risk and improve trust in optimization results for end users and downstream pipelines.
February 2025-01: SciPy optimization improvements focused on reliability, parity, and maintainability. Delivered standardized callback handling and result interpretation across multiple optimizers (dogbox, least_squares, trf), and strengthened the least_squares test suite to improve coverage, readability, and performance. These changes reduce regression risk and improve trust in optimization results for end users and downstream pipelines.
December 2024: Delivered scalable parallelization for approx_derivative in scipy/scipy and strengthened the reliability and visibility of parallel optimization workflows. Implemented worker-based processing using MapWrapper and HessWrapper, enhanced monitoring of function evaluations (nfev), and extended workers keyword support to multiple solvers. Built a robust test and documentation suite with multiprocess examples, while performing maintenance to reduce cruft and dependencies. Result: faster derivative calculations, improved solver throughput, and clearer developer usage signals, enabling teams to scale optimization workloads with confidence. Also completed dependency cleanup (scipy.misc), docstring refinements, and stability-focused test improvements to reduce regressions.
December 2024: Delivered scalable parallelization for approx_derivative in scipy/scipy and strengthened the reliability and visibility of parallel optimization workflows. Implemented worker-based processing using MapWrapper and HessWrapper, enhanced monitoring of function evaluations (nfev), and extended workers keyword support to multiple solvers. Built a robust test and documentation suite with multiprocess examples, while performing maintenance to reduce cruft and dependencies. Result: faster derivative calculations, improved solver throughput, and clearer developer usage signals, enabling teams to scale optimization workloads with confidence. Also completed dependency cleanup (scipy.misc), docstring refinements, and stability-focused test improvements to reduce regressions.
November 2024: RNG API enhancement delivered for numpy/numpy, focusing on performance and compatibility. Implemented default_rng to coerce RandomState to Generator and refactored RNG usage to leverage RandomState._bit_generator directly, resulting in clearer code paths and potential runtime efficiency gains. No major bugs fixed within this scope; the changes reduce long-term bug surface by simplifying RNG flow and improving API consistency. Overall impact includes faster RNG-dependent workloads, stronger API guarantees, and groundwork for future optimizations. Demonstrates proficiency in Python internals, API design, and performance-focused refactoring.
November 2024: RNG API enhancement delivered for numpy/numpy, focusing on performance and compatibility. Implemented default_rng to coerce RandomState to Generator and refactored RNG usage to leverage RandomState._bit_generator directly, resulting in clearer code paths and potential runtime efficiency gains. No major bugs fixed within this scope; the changes reduce long-term bug surface by simplifying RNG flow and improving API consistency. Overall impact includes faster RNG-dependent workloads, stronger API guarantees, and groundwork for future optimizations. Demonstrates proficiency in Python internals, API design, and performance-focused refactoring.

Overview of all repositories you've contributed to across your timeline