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Sungjoon Shon

PROFILE

Sungjoon Shon

Over 14 months, this developer advanced distributed AI model infrastructure across tenstorrent repositories, focusing on scalable inference, sharding, and performance optimization. They engineered features such as sparse Mixture-of-Experts support, streaming inference for DeepSeek-V4, and robust sharding propagation in tt-mlir and tt-xla, leveraging C++, Python, and MLIR. Their work included memory management fixes, backend integration with HuggingFace MoE, and enhancements for multi-device execution. By addressing edge-case bugs, optimizing tensor operations, and stabilizing CI pipelines, they improved reliability and throughput for large-scale model deployments, demonstrating depth in compiler design, backend development, and distributed systems engineering within production environments.

Overall Statistics

Feature vs Bugs

60%Features

Repository Contributions

60Total
Bugs
17
Commits
60
Features
25
Lines of code
19,732
Activity Months14

Work History

June 2026

10 Commits • 3 Features

Jun 1, 2026

June 2026 monthly summary for tenstorrent repositories tt-xla and tt-mlir. Focused on delivering scalable model inference, expanding MoE support, and stabilizing CI/regressions to improve reliability and business value. Key features delivered: - DeepSeek-V4 streaming inference: implemented layer-by-layer streaming for DeepSeek-V4-Flash with end-to-end tests; added input shard pinning to stabilize warmup and execution phases. - MoE backend integration from HuggingFace: introduced modular HF-backed MOE routing with 2D mesh support; added new tt_torch modules for moe_dense and attention backends; removed legacy monkey patches to enable HF dispatching. - Gemma-4 26B-A4B MoE support for vLLM on a 2D mesh: added TT-fused MoE routing, 2D mesh partitioning, and relevant closures/patch fixes to enable real-expert parallelism. - Mesh topology stability and tokenizer loading fixes: opened a 2D (4,8) parent mesh for BH Galaxy to mitigate MGD topology failures; updated tokenizer loading to prevent crashes in DeepSeek-V4 flows. - Test stability and validation improvements: removed xfail in mistral vLLM tests; reduced DeepSeek-V4 PCC end-to-end depth to 10 layers to avoid CI timeouts; added a CPU-reference PCC check and verbose decoding logs to surface output quality in CI. Major impact: enabled memory-efficient streaming for large models, broadened MoE support across HF and vLLM stacks, and reduced CI churn with targeted stability improvements. Demonstrated expertise in distributed runtime design, MoE routing, tokenizer resilience, and test automation. Technologies/skills demonstrated: - Layered streaming inference, end-to-end testing, and input shard management. - HuggingFace MoE backend integration, 2D mesh routing, and module modularization. - TT-Metal/tt-xla integration considerations with 2D mesh partitioning and global mesh registration. - BH Galaxy topology resilience and tokenizer robustness. - CI stabilization, performance regression analysis, and PCC validation.

May 2026

9 Commits • 5 Features

May 1, 2026

May 2026 monthly summary focusing on stability, scale-up readiness, and model support; delivered memory-management fixes, MoE/DeepSeek enhancements, and compile-time optimizations across tt-xla and tt-mlir to boost reliability and business value. Key features include A2aSparseMLP padding for small batches, DeepSeek-V4 MoE integration, a build-time memory option for const-eval inputs, Gemma-4 text-only inference with cross-layer KV sharing, and enhanced MoE testing with real weights. In tt-mlir, L1-overflow handling for fused concatenate_heads, a performance-oriented ConstevalForwardAnalysis, and a stability workaround for large head_dim in SDPA decode. These changes reduce runtime failures, enable larger models, speed up compilation, and improve test fidelity.

April 2026

5 Commits • 4 Features

Apr 1, 2026

April 2026 highlights: Implemented foundational improvements across TT MLIR and XLA backends to boost performance, stability, and model scalability. Replaced custom CCL canonicalization with SDY built-in patterns and added a post-canonicalization dead-op elimination in tt-mlir, reducing unnecessary work and preventing pattern-matching failures in StableHLO-to-TTIR. Propagated output_shard_dim through the full pipeline for AllToAllCombineOp, enabling consistent shard control from frontend to runtime. Introduced optional per-operation device synchronization for debugging asynchronous execution, with zero-overhead in release builds. In tt-xla, extended sparse MoE support to GLM-4, DeepSeek V3, and Kimi K2, including router unification, deduplication, and a new GLM-4 MoE layer test, setting the stage for improved model throughput and scalability.

March 2026

7 Commits • 2 Features

Mar 1, 2026

March 2026 highlights: Delivered scalable Sparse MoE support across TT-MLIR and TT-XLA, enabling sparse computations on multi-device meshes and end-to-end paths from StableHLO to runtime. Key features include Sparse MoE ops (sparse_matmul, all_to_all dispatch/combine, moe_expert_remap) and the SparseMLP module with extended sharding and a testing flag for dynamic MoE layer replacement. Implemented memory-efficient path for GPT OSS 120B nightly tests by delegating CPU golden path to the original expert implementation, reducing peak memory. Improved reliability and thread-safety with a PjrtTensorPool race-condition fix. Stabilized runtime by disabling approximate exponential mode for Blackhole SDPA decode to avoid compile failures. These workstreams collectively improve model scale, test reliability, and performance in production-like workloads while reducing risk in large-scale MoE deployments.

February 2026

1 Commits • 1 Features

Feb 1, 2026

February 2026 monthly summary for tt-mlir: Implemented Safe Sharding for Periodic Non-Splat Tensors, enabling safe sharding of periodic constants along the sharding axis and addressing a prior limitation in GlobalToLocalShape. This work is captured in commit d02b89115ebc4d76a15a9746d9cf0c011d993bf3 and related to the issue #6928. Resulting changes set the foundation for more scalable distributed workloads by ensuring correctness when tensor values are periodic and broadcasted, reducing unnecessary data duplication while maintaining identical data slices across devices.

January 2026

1 Commits

Jan 1, 2026

Month: 2026-01 — Key accomplishment: fix gather sharding axis conflict in tenstorrent/tt-mlir by changing the gather sharding rule from all-reduce to all-gather before the gather operation for collapsed_slice_dims, ensuring correctness and stability of sharded paths. Impact: prevents runtime errors caused by axis overlap, improves reliability of distributed training workloads, and aligns sharding behavior with replication expectations. Technical notes: commit 918ff6ebd0cb8f8873d8674280b1e4a063a9c8d0 implements the change (kReduction -> kNeedReplication) for collapsed_slice_dims to perform all-gather before the gather.

December 2025

6 Commits • 4 Features

Dec 1, 2025

December 2025 monthly summary: Implemented cross-repo improvements that boost performance, scalability, and interoperability. Key work includes sharding system enhancements and accurate sharding propagation in tt-mlir, an explicit CSE pass in StableHLO to TTIR lowering, vLLM multi-batch support with AscendScheduler in tt-xla, and a user-facing sharding constraints API for intermediate tensors. These changes improve distributed execution, reduce redundant ops, and enable more predictable multi-user workloads across Torch/Torch-XLA integrations.

November 2025

4 Commits • 1 Features

Nov 1, 2025

November 2025 focused on strengthening multi-device compute capabilities and ensuring test reliability across tt-mlir and tt-xla. Delivered foundational sharding infrastructure: per-consumer broadcasting decoupling to avoid cross-path sharding constraints, sharding propagation through composite operations, and the ability to register custom sharding rules for non-built-in ops via the Shardy framework. In parallel, TT-XLA CI tests were stabilized by fixing a missing argument in nightly tests for llama_3_1_70b models.

October 2025

3 Commits • 1 Features

Oct 1, 2025

Month: 2025-10 This month focused on backend reliability and performance improvements for PyTorch/XLA and TT-XLA, delivering a key feature for PJRT backend customization, addressing critical dtype-promotion edge-cases in bfloat16 multiplications, and stabilizing multi-device execution workflows. The work enhances performance tuning capabilities, reduces runtime errors in distributed graphs, and improves test coverage to prevent regressions.

September 2025

1 Commits

Sep 1, 2025

September 2025: Delivered a targeted test-backend fix for tenstorrent/tt-xla to run on TT PJRT XLA backend by adding explicit device conversion for both the model and its inputs. The change ensures tests execute on TT PJRT instead of CPU, producing accurate performance signals and reliable benchmarking. This work strengthened CI validation and cross-hardware compatibility, demonstrating proficiency with PyTorch XLA, TT PJRT, and test automation.

August 2025

4 Commits • 1 Features

Aug 1, 2025

Performance-focused month for tenstorrent/tt-metal (2025-08). Delivered a fast-path optimization for concat_ndim to accelerate single-shard tensor concatenation by bypassing unnecessary shape and dimension checks, reducing per-call overhead in common workloads. Implemented via a focused set of commits (four) with messages describing the minimal-dimensional fast path. No major bugs fixed documented for this repo this month; effort concentrated on performance enhancement, code-path robustness, and maintainability. Overall impact includes improved throughput and lower latency for single-shard concat operations, contributing to better real-time and batch workloads. Skills demonstrated include low-level optimization, careful performance profiling, and disciplined commit hygiene.

July 2025

1 Commits • 1 Features

Jul 1, 2025

July 2025 Monthly Summary for tenstorrent/tt-torch: Delivered enhancements to the PCC (Precision Consistency Check) validation for Blackhole models, extended test coverage, and refined per-model PCC requirements to tolerate minor diffs without compromising correctness. Resolved key device-level issues related to bfloat16 usage and utilization, stabilizing validation on target hardware. These changes improve model validation reliability, reduce test flakiness, and enable safer, faster deployments across production workloads including AlbertMaskedLM and ResNet50.

June 2025

2 Commits

Jun 1, 2025

June 2025 monthly summary for tenstorrent/tt-torch focusing on test suite reliability and CI stability. Key outcomes include re-enabling clamp tests for integer bounds, adding explicit tests for integer and float bounds, and hardening the nightly pipeline by skipping PCC checks on select architectures and validating executor output shapes before reshaping. These improvements reduced CI flakiness, improved edge-case coverage, and accelerated safe release readiness. Technologies involved include Python, PyTorch, CI pipelines, and test frameworks. Business value: more reliable builds, faster feedback, and safer progress toward feature releases.

May 2025

6 Commits • 2 Features

May 1, 2025

May 2025 performance summary for repository tenstorrent/tt-torch focusing on reliability, throughput, and computation graph correctness. Key features delivered include PCC-based model accuracy safety with IR/NN fusing stability and program export optimization with intermediate caching. Major bugs fixed address data casting correctness and golden outputs fidelity across multi-chip models. This work delivers measurable business value by improving model reliability, reducing the risk of regressions, and increasing throughput for model deployment pipelines.

Activity

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Quality Metrics

Correctness92.2%
Maintainability82.6%
Architecture87.0%
Performance84.2%
AI Usage31.0%

Skills & Technologies

Programming Languages

C++CMakeDockerfileJSONMLIRPythonYAML

Technical Skills

AI Model OptimizationAPI DesignAlgorithm optimizationBackend DevelopmentC++C++ DevelopmentC++ developmentC++ programmingCI/CDCMakeCaching StrategiesCode OptimizationCompiler DesignCompiler DevelopmentCompiler design

Repositories Contributed To

5 repos

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

tenstorrent/tt-xla

Sep 2025 Jun 2026
8 Months active

Languages Used

PythonC++JSONYAML

Technical Skills

PyTorchTestingXLACompiler DevelopmentDistributed SystemsML Frameworks

tenstorrent/tt-mlir

Nov 2025 Jun 2026
8 Months active

Languages Used

C++MLIRPythonCMakeDockerfile

Technical Skills

C++ DevelopmentC++ developmentCustom OperationsMLIRShardingcompiler design

tenstorrent/tt-torch

May 2025 Jul 2025
3 Months active

Languages Used

C++Python

Technical Skills

Caching StrategiesCode OptimizationFull Stack DevelopmentGraph CompilationGraph ProcessingMLIR

tenstorrent/tt-metal

Aug 2025 Aug 2025
1 Month active

Languages Used

C++

Technical Skills

C++ developmentC++ programmingalgorithm designperformance optimizationtensor manipulation

pytorch/xla

Oct 2025 Oct 2025
1 Month active

Languages Used

C++Python

Technical Skills

API DesignBackend DevelopmentC++PyTorchPythonTensor Operations