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Sofija Kotarac

PROFILE

Sofija Kotarac

Stefan Kotarac developed advanced test infrastructure and kernel features for the tenstorrent/tt-llk and tt-metal repositories, focusing on robust validation and performance optimization for tensor operations. He engineered dynamic data format inference, expanded matmul and reduction kernel coverage, and introduced row- and column-wise reduction support, addressing both floating-point and integer data types. Using C++, Python, and Makefile, Stefan refactored test APIs, consolidated configuration management, and implemented synchronization primitives to improve reliability and maintainability. His work enabled efficient, extensible pipelines and reduced regression risk, demonstrating deep expertise in low-level programming, embedded systems, and automated testing for high-throughput hardware workflows.

Overall Statistics

Feature vs Bugs

90%Features

Repository Contributions

46Total
Bugs
2
Commits
46
Features
19
Lines of code
18,535
Activity Months13

Work History

April 2026

2 Commits • 1 Features

Apr 1, 2026

April 2026: Delivered critical bug fix and standardization improvements in tt-metal, enhancing correctness of tile face row indexing and aligning Quasar llk tensor definitions with bh/wh references. These changes improve reliability, cross-repo consistency, and maintainability, enabling smoother future optimizations.

March 2026

5 Commits • 2 Features

Mar 1, 2026

March 2026 summary: Performance-focused LLK improvements on tt-metal with a strong emphasis on enabling ResNet5 workloads, expanding fixed-point support, and improving data-path efficiency. Delivered feature-level enhancements, extensive test coverage, and behind-the-scenes architectural optimizations that reduce latency and improve throughput for LLK tilize/untilize paths and unpack-to-dest operations.

February 2026

1 Commits • 1 Features

Feb 1, 2026

February 2026 Monthly Summary for tenstorrent/tt-llk: Delivered a new SFPU Row Reduction Kernel for Sum, adding row-wise reduction capability to the SFPU alongside the existing column-wise functionality. This feature supports multiple data formats and tiling, improving numerical stability and performance for tensor operations, which is particularly beneficial for SDPA backward workflows in tt-train. Key achievements and scope: - Implemented Row Reduction Kernel for Sum on SFPU, enabling row-wise reductions and expanding the tensor operation repertoire. - Added multi-tile support for row reductions, enabling reductions across ct_dim and rt_dim for scalable performance on larger tensors. - Expanded data-type coverage to Float32, Float16_b, Float16, Int32, UInt32, and UInt16 to accommodate diverse workloads. - Improved numerical stability and performance for SDPA backward in tt-train by providing a robust FP32 row-wise reduction path. - Code contribution: d68eccd7d89b98f35afe712f71c2b755520e1f7b; ticket #1052; linked issue https://github.com/tenstorrent/tt-metal/issues/35055. Business impact: - Enables more robust and faster tensor reductions in training and inference pipelines, reducing reliance on CPU-side computation and improving throughput for workloads that rely on row-wise reductions. - Enhances SFPU capabilities, enabling broader use cases and smoother integration with SDPA backward paths. Technologies/skills demonstrated: - Kernel development for specialized SIMD/FPU units (SFPU) - Tile-based reduction algorithms and multi-dimensions - Multi-format data handling (FP32, FP16, and integer types) - Performance optimization and attention to numerical stability - Cross-repo collaboration and issue-tracking (ticket #1052)

December 2025

1 Commits • 1 Features

Dec 1, 2025

2025-12 monthly performance summary for tenstorrent/tt-llk. Delivered a specialized SFPU Min/Max Reduction Kernel that unifies the MIN and MAX code paths and adds Int32 support, significantly improving pipeline performance and integration with downstream workflows. Implemented critical RTL-related fixes and robust workarounds for blackhole scenarios to ensure correctness across edge cases. The work includes a dedicated Int32 path, new initialization and calculation helpers, and a single-tile (32x32) reduction flow designed to meet Ops team requirements while maintaining a clean, maintainable code path.

November 2025

4 Commits • 2 Features

Nov 1, 2025

November 2025 was focused on performance-oriented kernel reductions in Quasar LLK and establishing a rigorous testing baseline for the Quasar matmul API. Deliverables implemented in tenstorrent/tt-llk drove measurable efficiency gains, broader format support, and stronger test coverage, positioning pipelines for higher throughput and easier maintenance.

October 2025

3 Commits • 2 Features

Oct 1, 2025

October 2025 focused on correctness and performance improvements in the TT-LLK subsystem, with two major feature deliveries and a codebase refinement that enhances testability and maintainability. The changes deliver better accuracy for reductions across data formats, reduced memory traffic through pairwise processing, and a Python-enabled, streamlined approach to format inference and LLK parameter management. Business value includes more reliable analytics across mixed data formats, lower runtime latency due to optimized reductions, and a cleaner, more maintainable LLK parameter/configuration pathway for future format growth.

September 2025

2 Commits • 1 Features

Sep 1, 2025

Concise monthly summary for 2025-09 focused on the tt-llk repository. Delivered a targeted Matmul testing coverage enhancement covering DST_INDEX edge cases and tiny-tile/face configurations. Refactored the test configuration API to a class-based structure, expanding matmul test scenarios while reducing total test cases to preserve essential coverage. No critical bugs fixed this month; effort centered on test reliability, efficiency, and developer productivity. Impact includes improved reliability of the math core matmul functionality, faster iteration cycles, and clearer test design. Skills demonstrated include test architecture, API refactor, parameterized testing, and edge-case coverage optimization.

August 2025

4 Commits • 1 Features

Aug 1, 2025

August 2025 monthly summary for tenstorrent/tt-llk: Focused on expanding Matmul API testing to increase coverage and robustness, including multi-tile sweeps across transpose modes, throttle modes, stochastic rounding, and dynamic tiling. This work strengthens matmul functionality through deeper test coverage, better tooling, and more representative scenarios for production workloads.

July 2025

2 Commits • 1 Features

Jul 1, 2025

July 2025 Monthly Summary for tenstorrent/tt-llk: Delivered a consolidated feature—Robust Test Infrastructure and Dynamic Data Format Inference—by merging two commits into a single capability. This work strengthens reliability, coverage, and extensibility across L1-L1 pipelines. Key outcomes include enhanced test infrastructure with full format coverage, zeroing of rows with non-infinite values, and precision-loss handling in fused tests; a new data format inference model (2.0) that adapts dynamically to fused and unfused scenarios across multiple pipeline runs. The deliverables reduce test flakes, improve developer velocity, and lay groundwork for future pipeline variants. Technologies demonstrated include test infrastructure engineering, dynamic inference modeling, and cross-pipeline validation.

June 2025

7 Commits • 2 Features

Jun 1, 2025

June 2025: Expanded Matmul test infrastructure and data-format coverage, added a fused Matmul + Unary SFPU test case, and strengthened test reliability and maintainability to reduce regression risk and accelerate data-format support.

May 2025

6 Commits • 2 Features

May 1, 2025

May 2025 monthly summary for tenstorrent/tt-llk focused on stabilizing the testing infrastructure and expanding data-format coverage to improve validation across formats and end-to-end processing paths. Delivered automated test utilities, eliminated flaky test plugins, and added kernel init/uninit support to the test suite, enabling more reliable QA and faster feedback loops. Achieved broader Matmul coverage through fusion testing and data-format robustness, strengthening confidence in performance-critical paths and release readiness.

April 2025

5 Commits • 2 Features

Apr 1, 2025

April 2025 monthly summary for tenstorrent/tt-llk focused on reliability, data handling, and flexible data formats. Delivered two key features with robust testing and cross-architecture support, improving validation, performance readiness, and data portability across tensor workloads.

March 2025

4 Commits • 1 Features

Mar 1, 2025

March 2025: Delivered targeted improvements to the tt-llk test infrastructure and resolved a critical synchronization race in the test pipeline, enabling more reliable and configurable validation of complex data flows. The work accelerates testing throughput and reduces debugging time for LLK-based workflows.

Activity

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Quality Metrics

Correctness90.4%
Maintainability83.6%
Architecture84.8%
Performance80.8%
AI Usage27.0%

Skills & Technologies

Programming Languages

C++HaskellMakefilePythonShellText

Technical Skills

API DesignAPI TestingAPI designBackend DevelopmentBug FixingC++C++ DevelopmentC++ developmentCI/CDCode OrganizationCode RefactoringConfiguration ManagementData EngineeringData Format HandlingData Format Inference

Repositories Contributed To

2 repos

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

tenstorrent/tt-llk

Mar 2025 Feb 2026
11 Months active

Languages Used

C++MakefilePythonTextHaskellShell

Technical Skills

Bug FixingC++C++ DevelopmentCI/CDConfiguration ManagementData Formats

tenstorrent/tt-metal

Mar 2026 Apr 2026
2 Months active

Languages Used

C++Python

Technical Skills

C++C++ developmentData ProcessingMachine LearningPythonPython Testing