{"slug": "an-ai-case-study-qdldl-fortran", "title": "An AI case study: qdldl-fortran", "summary": "Developer Jacob Williams used Claude Opus 5.5 to port the QDLDL sparse linear algebra C library to Fortran, publishing the result as qdldl-fortran on GitHub. The AI wrote the Fortran conversion and unit tests validating the results against the original C, and benchmarked both, with the Fortran version running slightly faster. Williams said he did not touch the code and pulled the library into his other project as an FPM dependency in less than an hour.", "body_md": "I needed some sparse linear algebra code for a project (more on that later). Using AI (Claude Opus 5.5), it suggested I just convert [qdldl](https://github.com/osqp/qdldl) to Fortran. I had never seen this library before, but it looked like a pretty straightforward C code. So, I had the AI develop a plan for converting it to Fortran and making it an FPM package.\n\nThe result is here: [GitHub - jacobwilliams/qdldl-fortran: Modern Fortran edition of QDLDL · GitHub](https://github.com/jacobwilliams/qdldl-fortran)\n\nIt’s pretty amazing. I haven’t touched the code at all. The AI ported it over to Fortran, and wrote unit tests to validate the results. I suggested it build the original C and compare the timings, and it did all that too. Note that the Fortran is a little bit faster in general. In less than an hour I was able to pull it in as a dependency (via FPM) into my other project and continue what I was doing, and it seems to be working great.", "url": "https://wpnews.pro/news/an-ai-case-study-qdldl-fortran", "canonical_source": "https://fortran-lang.discourse.group/t/an-ai-case-study-qdldl-fortran/11152#post_1", "published_at": "2026-10-04 16:06:43+00:00", "updated_at": "2026-10-04 16:10:33.406643+00:00", "lang": "en", "topics": ["developer-tools", "ai-tools", "artificial-intelligence"], "entities": ["Jacob Williams", "Claude Opus 5.5", "QDLDL", "qdldl-fortran", "Fortran", "GitHub", "FPM"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/an-ai-case-study-qdldl-fortran", "markdown": "https://wpnews.pro/news/an-ai-case-study-qdldl-fortran.md", "text": "https://wpnews.pro/news/an-ai-case-study-qdldl-fortran.txt", "jsonld": "https://wpnews.pro/news/an-ai-case-study-qdldl-fortran.jsonld"}}