terrapower/armi
Dec 2024 – Oct 2025
9 Months active
Languages Used
PythonRST
Technical Skills
Algorithm DesignCode Quality ImprovementCode RefactoringDocumentationRefactoringUnit Testing
Drew Johnson
PROFILE
Drew Johnson
Andrew Johnson contributed to the terrapower/armi repository by developing and refining core features for reactor simulation and data management. He focused on improving memory efficiency and reliability through iterator-based traversal, robust pin indexing, and enhanced database loading logic, all implemented in Python with careful use of data structures and object-oriented design. His work addressed challenges in numerical robustness, parallel computing with MPI, and data integrity for large-scale simulations. By introducing configuration management settings and strengthening test coverage, Andrew ensured maintainable, scalable workflows. The depth of his engineering is evident in his systematic refactoring and attention to correctness across complex simulation scenarios.
Overall Statistics
Feature vs Bugs
57%Features
Repository Contributions
23Total
Bugs
9
Commits
23
Features
12
Lines of code
4,299
Activity Months9
Your Network
15 people
Work History
October 2025
3 Commits • 2 Features
Oct 1, 2025October 2025 highlights for terrapower/armi focused on reliability, configurability, and maintainability. Delivered two targeted features and fixed a critical cross-section loading bug, with documentation improvements that clarify zone customization. Impact includes more reliable restarts, safer XS loading, and clearer configuration pathways for reactor zones. Demonstrated strong Python refactoring, interface design, and documentation skills, delivering tangible business value by reducing restart risk, enabling easier customization, and improving maintainability.
3 Commits • 2 Features
Oct 1, 2025October 2025 highlights for terrapower/armi focused on reliability, configurability, and maintainability. Delivered two targeted features and fixed a critical cross-section loading bug, with documentation improvements that clarify zone customization. Impact includes more reliable restarts, safer XS loading, and clearer configuration pathways for reactor zones. Demonstrated strong Python refactoring, interface design, and documentation skills, delivering tangible business value by reducing restart risk, enabling easier customization, and improving maintainability.
October 2025
September 2025
4 Commits • 1 Features
Sep 1, 2025September 2025 monthly summary for terrapower/armi: Focused on reliability and data integrity in geometry and pin-index management. Delivered Robust Pin Index Assignment for Spatial Blocks, including sorting-resilient logic, handling mixed fuel/non-fuel grids, and clearing previous pinIndices; added tests to verify behavior. Fixed CoordinateLocation persistence on load to guarantee accurate reconstruction of spatial relationships when saving/loading reactor models. These changes improve accuracy of simulations, reduce risk of data corruption during reordering, and enhance test coverage. Technologies demonstrated include Python code changes, test-driven development, and DB loading integrity.
September 2025
4 Commits • 1 Features
Sep 1, 2025September 2025 monthly summary for terrapower/armi: Focused on reliability and data integrity in geometry and pin-index management. Delivered Robust Pin Index Assignment for Spatial Blocks, including sorting-resilient logic, handling mixed fuel/non-fuel grids, and clearing previous pinIndices; added tests to verify behavior. Fixed CoordinateLocation persistence on load to guarantee accurate reconstruction of spatial relationships when saving/loading reactor models. These changes improve accuracy of simulations, reduce risk of data corruption during reordering, and enhance test coverage. Technologies demonstrated include Python code changes, test-driven development, and DB loading integrity.
August 2025
7 Commits • 5 Features
Aug 1, 2025August 2025 monthly summary for terrapower/armi: Focused on data-model simplification, robust pin-indexing, and improved data reconciliation. Delivered multiple data-model cleanups to reduce maintenance surface and potential misconfigurations. Enhanced pin indexing with per-component pinIndices and a block-level fallback to ensure accurate pin-tracking across rotations and configurations. Strengthened test reliability and correctness with concrete equality/hash fixes and unique test identifiers. Improved database comparison to correctly diff dictionaries and datasets of differing sizes, enabling more reliable state comparisons. Business value: cleaner data models reduce onboarding and maintenance costs; more accurate pin mappings improve simulation fidelity and configuration confidence; robust diffs speed issue diagnosis and reduce drift between expected and actual results; improved test hygiene lowers CI flakiness and accelerates iteration. Technologies/skills demonstrated: Python data modeling and refactoring, mapping algorithms, rotation-aware data structures, defensive programming for tests, and enhanced data-diff tooling.
7 Commits • 5 Features
Aug 1, 2025August 2025 monthly summary for terrapower/armi: Focused on data-model simplification, robust pin-indexing, and improved data reconciliation. Delivered multiple data-model cleanups to reduce maintenance surface and potential misconfigurations. Enhanced pin indexing with per-component pinIndices and a block-level fallback to ensure accurate pin-tracking across rotations and configurations. Strengthened test reliability and correctness with concrete equality/hash fixes and unique test identifiers. Improved database comparison to correctly diff dictionaries and datasets of differing sizes, enabling more reliable state comparisons. Business value: cleaner data models reduce onboarding and maintenance costs; more accurate pin mappings improve simulation fidelity and configuration confidence; robust diffs speed issue diagnosis and reduce drift between expected and actual results; improved test hygiene lowers CI flakiness and accelerates iteration. Technologies/skills demonstrated: Python data modeling and refactoring, mapping algorithms, rotation-aware data structures, defensive programming for tests, and enhanced data-diff tooling.
August 2025
July 2025
1 Commits
Jul 1, 2025Monthly summary for 2025-07: Delivered a critical data integrity fix in terrapower/armi by updating the Geodst file reader to use 32-bit integers, preventing truncation and overflow for large values and ensuring accurate representation of inputs. This change addresses larger datasets and reduces the risk of incorrect simulations and downstream errors. The commit implementing the change is 73b8629f8291004289378f0fcc1cbedb2b3c8a21. The work demonstrates solid data-type handling, Python/NumPy proficiency, and contributes to the reliability of geodst-based workflows.
July 2025
1 Commits
Jul 1, 2025Monthly summary for 2025-07: Delivered a critical data integrity fix in terrapower/armi by updating the Geodst file reader to use 32-bit integers, preventing truncation and overflow for large values and ensuring accurate representation of inputs. This change addresses larger datasets and reduces the risk of incorrect simulations and downstream errors. The commit implementing the change is 73b8629f8291004289378f0fcc1cbedb2b3c8a21. The work demonstrates solid data-type handling, Python/NumPy proficiency, and contributes to the reliability of geodst-based workflows.
May 2025
1 Commits • 1 Features
May 1, 2025May 2025 monthly summary for terrapower/armi: Delivered feature to automatically expand a reactor to its full core configuration on database load, gated by a new setting to prevent unnecessary expansion. Updated database loading logic to respect the setting and added tests to verify correct behavior. These changes reduce unnecessary work during startup/load and improve reliability of core configuration loading.
1 Commits • 1 Features
May 1, 2025May 2025 monthly summary for terrapower/armi: Delivered feature to automatically expand a reactor to its full core configuration on database load, gated by a new setting to prevent unnecessary expansion. Updated database loading logic to respect the setting and added tests to verify correct behavior. These changes reduce unnecessary work during startup/load and improve reliability of core configuration loading.
May 2025
April 2025
2 Commits • 1 Features
Apr 1, 2025In April 2025, terrapower/armi delivered key improvements focused on memory-efficient iteration and MPI shutdown efficiency. The team introduced iterator-based block traversal and reduced unnecessary inter-process communication, resulting in performance gains and easier maintenance. These changes lay groundwork for scalable simulations and improved developer velocity.
April 2025
2 Commits • 1 Features
Apr 1, 2025In April 2025, terrapower/armi delivered key improvements focused on memory-efficient iteration and MPI shutdown efficiency. The team introduced iterator-based block traversal and reduced unnecessary inter-process communication, resulting in performance gains and easier maintenance. These changes lay groundwork for scalable simulations and improved developer velocity.
March 2025
1 Commits • 1 Features
Mar 1, 2025March 2025 monthly summary focused on delivering a key performance improvement in the ARMI framework.
1 Commits • 1 Features
Mar 1, 2025March 2025 monthly summary focused on delivering a key performance improvement in the ARMI framework.
March 2025
February 2025
2 Commits
Feb 1, 2025February 2025 – terrapower/armi: Delivered targeted fixes to improve numerical robustness and reduce noise in simulation output. Key work included HexGrid improved rotated index detection with a relative pitch tolerance and suppression of density warnings for Component Fluids, both accompanied by dedicated tests ensuring correct behavior under floating-point variations and material conditions. These changes enhance reliability of grid indexing and material handling, lower maintenance cost due to warning noise, and support more trustworthy downstream analyses.
February 2025
2 Commits
Feb 1, 2025February 2025 – terrapower/armi: Delivered targeted fixes to improve numerical robustness and reduce noise in simulation output. Key work included HexGrid improved rotated index detection with a relative pitch tolerance and suppression of density warnings for Component Fluids, both accompanied by dedicated tests ensuring correct behavior under floating-point variations and material conditions. These changes enhance reliability of grid indexing and material handling, lower maintenance cost due to warning noise, and support more trustworthy downstream analyses.
December 2024
2 Commits • 1 Features
Dec 1, 2024December 2024 monthly work summary focused on terrapower/armi, highlighting key features delivered, major bugs fixed, and overall impact. The work emphasizes business value through improved correctness, reliability, and maintainability of the rotation/orientation functionality and its tests.
2 Commits • 1 Features
Dec 1, 2024December 2024 monthly work summary focused on terrapower/armi, highlighting key features delivered, major bugs fixed, and overall impact. The work emphasizes business value through improved correctness, reliability, and maintainability of the rotation/orientation functionality and its tests.
December 2024
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Quality Metrics
Correctness91.8%
Maintainability91.8%
Architecture89.2%
Performance83.0%
AI Usage21.8%
Skills & Technologies
Programming Languages
PythonRST
Technical Skills
API DesignAlgorithm DesignCode OptimizationCode Quality ImprovementCode RefactoringComponent DesignComponent ManagementConfiguration ManagementCore DevelopmentData HandlingData StructuresDatabase ComparisonDatabase ManagementDocumentationError Handling
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