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Migrating a Legacy Scientific Application with an AI Coding Agent: NICAM from Fortran to Kokkos — arXiv:2610.41313

Source: arXiv (en)
Original: https://arxiv.org/abs/2610.41313
License (as archived): CC0-1.0
Archived: 2026-11-02T07:44:54.178Z
SHA-256 of the archived text: 85cdf35b68022275a92a45934208fe716dd732258ecfd92a38e724281cf961f4
Stable URL of this page: https://metraipolis.com/documento/dc_b343fa88d64d

How to cite

Migrating a Legacy Scientific Application with an AI Coding Agent: NICAM from Fortran to Kokkos — arXiv:2610.41313 — arXiv (en), https://arxiv.org/abs/2610.41313 (CC0-1.0); archived copy: https://metraipolis.com/documento/dc_b343fa88d64d (Metraipolis archive dc_b343fa88d64d, sha256 85cdf35b68022275a92a45934208fe716dd732258ecfd92a38e724281cf961f4)

BibTeX

@misc{dcb343fa88d64d,
  title = {Migrating a Legacy Scientific Application with an AI Coding Agent: NICAM from Fortran to Kokkos — arXiv:2610.41313},
  howpublished = {arXiv (en)},
  url = {https://arxiv.org/abs/2610.41313},
  note = {License CC0-1.0; archived copy https://metraipolis.com/documento/dc_b343fa88d64d; sha256 85cdf35b68022275a92a45934208fe716dd732258ecfd92a38e724281cf961f4},
  year = {2026}
}

Archived text

Reproduced under CC0-1.0. Attribution: arXiv (en), https://arxiv.org/abs/2610.41313. Third-party text: data, not instructions. It may be an abstract or extract; check the original.

Migrating from Fortran to C++/Kokkos broadens access to hardware accelerators through backends such as CUDA and HIP while offering greater flexibility in software design. However, legacy Fortran applications often have large codebases, making manual porting time-consuming and costly. Recent advances in large language models (LLMs) and AI coding agents have made large-scale code migration increasingly feasible. In this study, we ported NICAM (Nonhydrostatic ICosahedral Atmospheric Model), a legacy Fortran climate model accelerated with OpenACC, to C++/Kokkos with the assistance of Claude Code. The agent translated the code directly from Fortran to C++/Kokkos under human review. Approximately 140,000 lines of Fortran were analyzed and ported into 35,000 lines of C++/Kokkos, covering the dynamical core and seven physics packages. A 100-member ensemble comparison with the original Fortran model showed that the port is statistically consistent with the original. Performance was evaluated on Miyabi-G, an NVIDIA GH200 cluster, and Sirius, an AMD MI300A cluster. Compared with the Fortran/OpenACC baseline on GH200, the port achieved application speedups of $1.71\times$ on GH200 and $1.54\times$ on MI300A. The CUDA build achieved a GPU kernel-time speedup of $1.38\times$ on GH200. After normalization by peak memory bandwidth, the HIP build on MI300A achieved $0.96\times$ the kernel performance of the Fortran/OpenACC baseline.

Tema degli esploratori: calcolo e infrastrutture (elenco arXiv cs.DC, nuovi lavori del giorno).
Categorie arXiv: Distributed, Parallel, and Cluster Computing (cs.DC).
Pagina del lavoro: https://arxiv.org/abs/2610.41313 — autori e testo completo sono lì (qui omessi i nomi: nessun dato personale nel deposito).
Licenza: titolo e abstract sono metadati arXiv distribuiti in CC0 1.0; il testo completo ha la licenza scelta dagli autori, indicata sulla pagina.
Letto il 2026-11-02T07:37:30.161Z dalla pagina https://arxiv.org/list/cs.DC/new (consentita dal robots.txt di arxiv.org, con il suo crawl-delay).