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Optimization of MuMax3 by Using Claude Code: A CUDA-Graph-Based Case Study in AI-Assisted Performance Engineering

2026-05-31T15:00:00Z

Title: Optimization of MuMax3 by Using Claude Code: A CUDA-Graph-Based Case Study in AI-Assisted Performance Engineering Author(s): You, Chun-Yeol Abstract: MuMax3 is a widely used open-source GPU-accelerated micromagnetic simulator whose computational core - CUDA kernels and cuFFT-based demagnetization convolutions - has changed little since its original release. We report a case study in which an agentic large-language-model coding assistant (Claude Code, Anthropic) was used, under continuous human supervision, to profile and optimize this mature CUDA/Go codebase. Profiling with NVIDIA Nsight Systems revealed that for small and medium grids (64 & times;64 & times;1 to 256 & times;256 & times;1 cells), 75-79 % of step time is spent in CPU-side cuLaunchKernel driver calls rather than in GPU computation, because every solver step launches roughly 27 kernels sequentially on a single CUDA stream. Building on this finding, we implemented a "split-graph" execution strategy: the time-step-independent torque-evaluation kernel sequences of each solver stage are captured once as CUDA Graphs and replayed via cudaGraphLaunch, while the time-step-dependent update, error estimate, and adaptive-step-size logic remain ordinary stream-ordered calls. The optimization is exposed transparently through Run()/Steps(), guarded by a compatibility check (constant excitation, zero thermal field, no custom field terms, time-independent material parameters, mesh size below a tunable threshold) that falls back silently to the original code path when violated. Across five solvers (Heun, RK23, RK45DP, RK56, Backward Euler), the optimization yields up to 5.4 & times; throughput for a 64 & times;64 & times;1 grid with a fixed time step, 2.4-3.6 & times; for adaptive time-stepping, decreasing smoothly to approximate to 1.0 & times; near 10(6) cells, essentially independent of which physical field terms (exchange, anisotropy, DMI) are active. All results were verified bit-for-bit identical (ndiff=0) against the unmodified code, and the full 176-script mumax3 regression suite passes with zero failures. We discuss the workflow itself - including three episodes in which the assistant autonomously diagnosed and corrected its own defects - as a template for AI-assisted optimization of legacy scientific HPC codes.

사파이어 미스컷 기판을 이용한 무자기장 스핀궤도토크 스위칭 소자

Title: 사파이어 미스컷 기판을 이용한 무자기장 스핀궤도토크 스위칭 소자 Author(s): 김진아; 유천열; 안수혁

체성분 분석을 위한 초음파 영상 시스템 및 초음파 영상 시스템의 동작 방법

Title: 체성분 분석을 위한 초음파 영상 시스템 및 초음파 영상 시스템의 동작 방법 Author(s): 유천열; 이문환; 황재윤 Abstract: 대상체에 대한 복수의 위치에서 대상체로 초음파 신호를 송신하고 그로부터 반사된 신호를 수신 가능한 스캔 장치를 이용하여, 대상체의 3차원 초음파 영상을 용이하게 생성하는 체성분 분석을 위한 초음파 영상 시스템 및 초음파 영상 시스템의 동작 방법이 개시된다. 초음파 영상 시스템은 대상체를 삽입 가능한 스캔 장치와, 상기 스캔 장치의 일부에 연결된 초음파 탐촉자와, 상기 초음파 탐촉자로 하여금 상기 스캔 장치에 대하여 복수의 위치에서 상기 대상체로 송신 초음파 신호를 발생시키고, 상기 대상체로부터 반사된 반사 초음파 신호를 수신하도록 제어하는 제어부와, 상기 스캔 장치에 대한 복수의 위치에서 각각 수신된 상기 반사 초음파 신호에 기초하여 복수의 2D 초음파 영상을 생성하고, 상기 복수의 2D 초음파 영상에 기초하여 3D 초음파 영상을 생성하는 영상 처리부를 포함할 수 있다.

Deterministic spin-orbit torque switching of epitaxial ferrimagnetic insulator with perpendicular magnetic anisotropy fabricated by on-axis magnetron sputtering

2025-09-30T15:00:00Z

Title: Deterministic spin-orbit torque switching of epitaxial ferrimagnetic insulator with perpendicular magnetic anisotropy fabricated by on-axis magnetron sputtering Author(s): Ngaloy, Roselle T.; Yamashita, Naoto; Zhao, Bing; Kim, Soojung; Yamashita, Kohei; Cools, Ivo P.C.; Agusutrisno, Marlis Nurut; Lee, Soobeom; Kurokawa, Yuichiro; You, Chun-Yeol; Yuasa, Hiromi; Dash, Saroj Prasad Abstract: Current-induced switching of magnetization states in ferromagnet/spin-orbit material heterostructures has attracted significant attention, driven by the increasing need for low power consumption and a more efficient mechanism for magnetization switching. However, current shunting for the used metallic ferromagnets remains challenging in achieving low switching current densities. Thulium iron garnet, Tm3Fe5O12 (TmIG), is promising for such devices as it exhibits strong perpendicular magnetic anisotropy (PMA) and fast magnetization dynamics. However, there still remains a technological challenge in the growth of TmIG films using industry-compatible magnetron sputtering in a simple on-axis geometry for spintronic device applications. Here, we demonstrated the spin-orbit torque (SOT) magnetization switching of TmIG thin film grown by on-axis radio-frequency magnetron sputtering. Robust and deterministic SOT magnetization switching is achieved using TmIG/Pt heterostructures at a current density as low as 0.7×1011A/m2. Anomalous Hall and second harmonic Hall measurements were performed to quantify effective spin-orbit fields. The effective field inducing damping-like torque is estimated to be 21±1 Oe per 107A/cm2, higher than previous reports. These findings show a growth method for ferrimagnetic insulators with strong PMA in industry-compatible on-axis sputtering methods and its utilization for achieving energy-efficient SOT non-volatile memory applications. © 2025 Elsevier B.V., All rights reserved.