June 2026 monthly summary for the ammarhakim/gkylzero repository. The work focused on stabilizing and extending the gyrokinetic cyclone base case, expanding data support for geometry and BGK source customization, improving GPU compatibility, and strengthening test coverage and code quality. These efforts reduce run-time risk, enable user-driven customization of BGK rates and equations, and improve maintainability for long-term science workflows.

May 2026 — Monthly summary for the ammarhakim/gkylzero repository. Focused on delivering user-facing features, improving cross-platform reliability (CPU/GPU), and strengthening test coverage to boost reproducibility and confidence in numerical results. Key features introduced include partial recycling support with adaptive sources and visible recycling factors, and a new tess_secret_option flag to control exposure of secret options. A 2D Maxwellian CBC initialization was added to support Canonical Maxwellian inputs, with notes on observed divergence behavior. Regression tests for CBC were enhanced to verify matrix reuse and solutions inside repetition loops, with updates to the regression suite and an adiabatic setup for future testing. Several bug fixes and maintenance improvements were applied to harden initialization, improve geometry handling, and clean up the codebase. Overall impact: greater reliability, clearer user controls, faster and more stable test cycles, and improved cross-platform parity. Technologies/skills demonstrated include C/C++ code health, regression testing, matrix reuse validation, GPU/CPU parity considerations, and feature flagging.

Month: 2026-03 — concise monthly summary focusing on business value and technical achievements. No new features released this month for ammarhakim/gkylzero; major work centered on a targeted bug fix to improve reliability and IO efficiency.

February 2026 monthly summary for the ammarhakim/gkylzero project. Focused on establishing a robust, reproducible developer workflow and expanding the test coverage for gyrokinetic sheath boundary conditions. Delivered a macOS-capable CI/CD/build pipeline, essential build tooling, and extended tests to support higher-dimensional velocity spaces with cross-CPU/GPU compatibility. These efforts improve maintainability, reduce integration risk, and increase confidence in boundary-condition implementations across CPU and GPU environments.

January 2026 monthly summary for ammarhakim/gkylzero: Delivered a feature that decouples periodicity from the field and ties it to species boundary conditions in the init_maxwellian_gaussian routine, improving simulation fidelity and configurability for gyrokinetic studies. This enables more accurate boundary-condition-driven experiments and reduces misconfiguration risk.

December 2025: Focused on stabilizing gyrokinetic calculations in ammarhakim/gkylzero. Implemented critical correctness fixes to ensure reliable simulation results and reduce downstream debugging effort. Delivered targeted code fixes with minimal risk to existing functionality, emphasizing numerical correctness and maintainability.

November 2025 monthly summary for ammarhakim/gkylzero focusing on correctness, stability, and physics fidelity across the gyrokinetic codebase. Delivered targeted bug fixes to align geometry definitions with gyrokinetic expectations, stabilized GPU projections, and enhanced temperature calculations for variable dimensionality. These efforts improved production reliability, reduced risk of runtime failures, and increased accuracy of simulated physics in production runs.

October 2025 focused on stabilizing the CUDA kernel build and improving code readability for the gkeyll project. Implemented a targeted fix to remove build-time warnings by inlining hardcoded array sizes in the rescale_ghost_jacf_advance_cu_ker kernel, resulting in more reliable compilation and easier maintenance. The work enhances GPU kernel robustness with minimal risk and supports smoother CI cycles and future enhancements.

September 2025 monthly summary for the ammarhakim/gkeyll repository: Delivered stability, diagnostics, and feature enhancements that improve reliability, performance, and physics fidelity. Focused on code quality, test robustness, and alignment of models with experimental values to accelerate developer feedback and deployment readiness.

August 2025 performance review summary for the ammarhakim/gkeyll project. The main focus was delivering a Discontinuous Galerkin (DG) shift-function representation for twist-shift, centralizing evaluation through ts_shift_eval, and laying the groundwork for broader DG adoption. The work also included substantial refactoring to improve accuracy, flexibility, and maintainability, plus targeted debugging to stabilize the twist-shift feature and prepare for production use.

July 2025: Delivered a critical bug fix in the CUDA kernel path of gkeyll, addressing an incorrect conditional multiplication in gkyl_prim_cross_m0deltas_set_op_range_cu_kernel (normNu path) and performing a minor signature formatting adjustment to gkyl_prim_cross_m0deltas_advance_cu. The change ensures correct application of nuself_d when up->normNu is true, improving numerical accuracy and stability for normNu-enabled simulations. Committed as d01c7ab6e553afa4c3c383dfe4684836f0ff38ff.

June 2025 monthly review for the ammarhakim/gkeyll repository focused on delivering robust adaptive source handling, GPU/memory improvements, and cleaner code, with an emphasis on reliability, performance, and business value. The work enhanced test coverage, stabilized restart behavior across grids, and refined projection and diagnostic capabilities, enabling more accurate, scalable gyrokinetic simulations while reducing maintenance risk.

In May 2025 (2025-05), the focus was on stabilizing and modernizing the adaptive source and boundary handling paths in the gkeyll codebase to improve reliability and scientific accuracy in production workloads. Key work targeted adaptive source stability, robust Gaussian projection in periodic domains, domain sizing for toroidal mode consistency, and refined boundary flux/conditions. The combination of these efforts reduced numerical edge cases, improved accuracy for rhostar in toroidal meshes, and strengthened GPU build readiness, enabling more reliable, repeatable simulations for research and production use.

April 2025: Delivered foundational improvements to the adaptive source pipeline, stabilized multi-GPU operation, and tightened memory/validation practices, while updating data profiles and naming conventions to improve maintainability and future proofing.

March 2025 performance snapshot: Strengthened core modeling capabilities and stability across gkeyll and gkylcas, enabling more accurate power control, faster integration cycles, and regression-tested features aligned with DR631. The work delivered in this month lays the foundation for more reliable simulations and smoother production runs, with explicit improvements in source adaptation, moment calculations, and CUDA kernel integration.

February 2025 (2025-02) monthly summary for ammarhakim/gkeyll focusing on boundary condition improvements, Poisson solver integration, and stability/maintenance work. Delivered configurable corner boundary handling, integrated bias planes with Poisson boundary, enhanced deflated Poisson interface, and re-enabled/Refactored TSBC/SSFG updaters with improved encapsulation. Stabilized memory usage and CUDA/toolkit compatibility, and accelerated testing and maintenance cycles.

January 2025 monthly summary for the ammarhakim/gkeyll project. This period delivered significant feature work, reliability fixes, and code quality improvements across the updater, Poisson solver, and ghost-to-skin surface workflows, enabling more robust 2x and 2x2v simulations and improving maintainability.

December 2024 performance summary for ammarhakim repositories (gkeyll and gkylcas) focusing on CPU/GPU integration, array averaging, and test framework improvements. The month centered on delivering core features, stabilizing the GPU path, expanding test coverage, and cleaning up architecture for maintainability and future performance gains.

For 2024-11, delivered and hardened Twist-Shift Boundary Conditions (TSBC) across the z-domain in the GK-phi framework, significantly improving boundary fidelity and stability for tokamak-scale simulations. Key boundary work includes phase 1 TSBC application to the GK electrostatic potential using the SSFG updater on the lower z-plane, enforcement of twist-shifticity at z-boundaries, corner constraint handling (including phi and GK corners), and updates to Poisson solver matrices and boundary application routines to support edge handling and z-edge constraints. Restored phase 5.1 for phi with targeted corner handling to address radial discontinuities. Implemented conducting-wall BC at the target corner (z=0, Lz, x=LCFS) as part of phase-1 TSBC, and refined the solver to account for global z-edges via is_z_edge flags and additional BCs. Accompanying this, the boundary-aware code paths were aligned with the DR issues (e.g., #504, #535) to ensure correctness across core boundary regions. In addition, expanded test coverage and infrastructure to validate the boundary and solver changes. Enhanced unit tests for skin-ghost surface data handling with varied ghost coefficients, and added flux-surface average tests that compare surface-integrated moments to full-volume integrals across a 3x2v setup. This includes grid and magnetic-field adjustments to ensure Jacobian stability and reliable comparisons. A dedicated memory safety improvement was completed in the integrated moments testing: a memory leak was fixed by ensuring proper release of marr_host and guarding GPU/host allocations during initialization and cleanup, improving reliability of GPU-accelerated test paths.

Deliverables during 2024-10 focused on gyrokinetic boundary conditions and code maintainability across two repos (ammarhakim/gkylzero and ammarhakim/gkeyll). In gkylzero, the Gyrokinetic Boundary Condition Updaters were refactored and initialization cleanup completed, introducing a new gk_field_apply_bc mechanism, simplifying updater interfaces, and ensuring boundary conditions are applied at the correct stage after species initialization. Documentation clarifications around skin-ghost handling were added to reduce ambiguity and potential misuses. In gkeyll, boundary condition handling stabilization fixed incorrect/duplicate application in the gk_field module, removing redundant calls to gk_field_apply_bc within calc_field_and_apply_bc and ensuring phi BCs are applied within calc_field. Additional readability improvements to skin_surf_from_ghost components were implemented to reduce maintenance risk. These changes collectively improve simulation accuracy, reliability, and maintainability, while clarifying usage patterns for boundary conditions and ghost handling.