
Alex Sepkowski developed and maintained advanced test infrastructure for the Esri/DirectXShaderCompiler repository, focusing on long-vector shader execution paths and Shader Model 6.9 readiness. Leveraging C++ and HLSL, Alex expanded coverage for derivative, reduction, and wave operations, refactored test suites for maintainability, and addressed reliability issues such as buffer alignment and floating-point tolerances. He improved build robustness by resolving compiler warnings and enhanced release processes through documentation and versioning updates. Alex’s work enabled earlier regression detection, reduced CI noise, and ensured stable shader compilation validation, demonstrating depth in debugging, test automation, and graphics programming within complex GPU development workflows.

January 2026 monthly summary for Esri/DirectXShaderCompiler. This period focused on stabilizing shader execution in complex derivative paths and advancing the Shader Model 6.9 release readiness. Key work included a bug fix for long vector derivative tests to prevent derivative sinking in conditionals, and comprehensive preparation for SM6.9 release through HLK testing updates, versioning scaffolding, and release process improvements. The combined efforts reduce risk for customers and streamline release communication, with deliverables spanning code stability, testing coverage, release artifacts, and documentation practices.
January 2026 monthly summary for Esri/DirectXShaderCompiler. This period focused on stabilizing shader execution in complex derivative paths and advancing the Shader Model 6.9 release readiness. Key work included a bug fix for long vector derivative tests to prevent derivative sinking in conditionals, and comprehensive preparation for SM6.9 release through HLK testing updates, versioning scaffolding, and release process improvements. The combined efforts reduce risk for customers and streamline release communication, with deliverables spanning code stability, testing coverage, release artifacts, and documentation practices.
December 2025 performance summary for Esri/DirectXShaderCompiler. The month focused on expanding test coverage for long-vector execution paths, tightening accuracy for half-precision trig-related tests, and improving build robustness by addressing compiler warnings in the LongVectors.cpp area. The combined results increase testing confidence, reduce noise in CI, and reinforce production-grade stability for shader compilation and execution validation.
December 2025 performance summary for Esri/DirectXShaderCompiler. The month focused on expanding test coverage for long-vector execution paths, tightening accuracy for half-precision trig-related tests, and improving build robustness by addressing compiler warnings in the LongVectors.cpp area. The combined results increase testing confidence, reduce noise in CI, and reinforce production-grade stability for shader compilation and execution validation.
Month: 2025-11 | Repository: Esri/DirectXShaderCompiler Key features delivered: - WaveActive long-vector testing framework and coverage expanded: added WaveActiveSum tests; initiated WaveActiveMin/Max/Prod; finished basic long-vector WaveOp tests; extended WaveMulti* coverage; included test helpers and off-by-one corrections to improve reliability. - LoadAndStoreOp tests reliability improvements: addressed buffer sizing, descriptor correctness, alignment handling, and compatibility with structured buffers to improve test accuracy. Major bugs fixed: - WaveActiveAllEqual correctness for bools; off-by-one bug in WaveActiveAllEqual resolved. - NFC-related fix: corrected typo in OP_CAST macro to ensure consistent test macros. Overall impact and accomplishments: - Significantly strengthened the test suite for long-vector and load/store pathways, increasing confidence in DirectXShaderCompiler behavior, enabling earlier regression detection, and reducing release risk. Technologies/skills demonstrated: - C++ test framework enhancements, regression testing, test helper engineering, alignment and descriptor handling, structured-buffer validation, and macro hygiene.
Month: 2025-11 | Repository: Esri/DirectXShaderCompiler Key features delivered: - WaveActive long-vector testing framework and coverage expanded: added WaveActiveSum tests; initiated WaveActiveMin/Max/Prod; finished basic long-vector WaveOp tests; extended WaveMulti* coverage; included test helpers and off-by-one corrections to improve reliability. - LoadAndStoreOp tests reliability improvements: addressed buffer sizing, descriptor correctness, alignment handling, and compatibility with structured buffers to improve test accuracy. Major bugs fixed: - WaveActiveAllEqual correctness for bools; off-by-one bug in WaveActiveAllEqual resolved. - NFC-related fix: corrected typo in OP_CAST macro to ensure consistent test macros. Overall impact and accomplishments: - Significantly strengthened the test suite for long-vector and load/store pathways, increasing confidence in DirectXShaderCompiler behavior, enabling earlier regression detection, and reducing release risk. Technologies/skills demonstrated: - C++ test framework enhancements, regression testing, test helper engineering, alignment and descriptor handling, structured-buffer validation, and macro hygiene.
Monthly performance summary for 2025-10 covering key deliverables in microsoft/DirectXShaderCompiler and microsoft/hlsl-specs. Emphasizes expanded test coverage, test infrastructure improvements, targeted bug fixes, and documentation alignment that reduce risk and accelerate validation before release.
Monthly performance summary for 2025-10 covering key deliverables in microsoft/DirectXShaderCompiler and microsoft/hlsl-specs. Emphasizes expanded test coverage, test infrastructure improvements, targeted bug fixes, and documentation alignment that reduce risk and accelerate validation before release.
September 2025 performance summary for microsoft/DirectXShaderCompiler. Key features delivered include expanded Long Vector test coverage across ternary, Ldexp/Frexp, binary operators, bitwise, unary, and cast operations, with alignment to the latest WARP. Also completed maintenance and refactor of the LongVectors test suite to enhance readability and maintainability. Major bugs fixed in long vector tests include AsTypeOp scalar flag parsing, trig function tolerances for float16, and correctness of split double expectations, improving accuracy and reliability. Overall impact: stronger validation coverage for long-vector shader paths, earlier regression detection, and more stable shader compilation validation under long-vector workloads. Technologies/skills demonstrated: C++ test infrastructure usage, test suite templating and NFC-oriented refactors, tolerance tuning for numerical tests, and ensuring compatibility with WARP in validation flows.
September 2025 performance summary for microsoft/DirectXShaderCompiler. Key features delivered include expanded Long Vector test coverage across ternary, Ldexp/Frexp, binary operators, bitwise, unary, and cast operations, with alignment to the latest WARP. Also completed maintenance and refactor of the LongVectors test suite to enhance readability and maintainability. Major bugs fixed in long vector tests include AsTypeOp scalar flag parsing, trig function tolerances for float16, and correctness of split double expectations, improving accuracy and reliability. Overall impact: stronger validation coverage for long-vector shader paths, earlier regression detection, and more stable shader compilation validation under long-vector workloads. Technologies/skills demonstrated: C++ test infrastructure usage, test suite templating and NFC-oriented refactors, tolerance tuning for numerical tests, and ensuring compatibility with WARP in validation flows.
August 2025 monthly summary: Delivered significant test infrastructure improvements and bug fixes across DirectXShaderCompiler and hlsl-specs, focusing on reliability, coverage, and traceability. Key outcomes include a refactor of the long vector test suite to OO design (removing .tpp usage) with expanded unary/binary coverage, a reliability bug fix in test parameter parsing, and an updated Long Vector Execution Test Plan to improve coverage mapping to DXIL/LLVM. Together these changes reduce flaky tests, accelerate validation, and demonstrate strong test engineering and metadata handling across C++ test suites.
August 2025 monthly summary: Delivered significant test infrastructure improvements and bug fixes across DirectXShaderCompiler and hlsl-specs, focusing on reliability, coverage, and traceability. Key outcomes include a refactor of the long vector test suite to OO design (removing .tpp usage) with expanded unary/binary coverage, a reliability bug fix in test parameter parsing, and an updated Long Vector Execution Test Plan to improve coverage mapping to DXIL/LLVM. Together these changes reduce flaky tests, accelerate validation, and demonstrate strong test engineering and metadata handling across C++ test suites.
In July 2025, I focused on strengthening the DirectXShaderCompiler’s testing foundation for long-vector HLSL operations within the libsdl-org/DirectXShaderCompiler repository. Delivered a consolidated long-vector tests framework with new helper types, expanded coverage across trig operations, type casting (AsType), and Split/MakeDouble functionality, plus targeted test stability improvements to reduce flaky results. Also fixed a shader source issue that caused out-of-bounds (OOB) access in ExecutionTests::AtomicsShared64Test and merged long-vector trig operation tests to enhance reliability and signal coverage. Business value: heightened confidence in shader correctness across long-vector scenarios, reduced defect leak in CI, and accelerated validation cycles for ongoing shader compiler improvements.
In July 2025, I focused on strengthening the DirectXShaderCompiler’s testing foundation for long-vector HLSL operations within the libsdl-org/DirectXShaderCompiler repository. Delivered a consolidated long-vector tests framework with new helper types, expanded coverage across trig operations, type casting (AsType), and Split/MakeDouble functionality, plus targeted test stability improvements to reduce flaky results. Also fixed a shader source issue that caused out-of-bounds (OOB) access in ExecutionTests::AtomicsShared64Test and merged long-vector trig operation tests to enhance reliability and signal coverage. Business value: heightened confidence in shader correctness across long-vector scenarios, reduced defect leak in CI, and accelerated validation cycles for ongoing shader compiler improvements.
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