https://ertu.dev/tags/jvm/ Recent content in Jvm on Ertu's Blog https://ertu.dev/%3Clink%20or%20path%20of%20image%20for%20opengraph,%20twitter-cards%3E https://ertu.dev/%3Clink%20or%20path%20of%20image%20for%20opengraph,%20twitter-cards%3E Hugo -- 0.140.2 en Thu, 11 Jun 2026 18:53:00 +0300 https://ertu.dev/posts/4_clojure-reaching-c-performance/ Thu, 11 Jun 2026 18:53:00 +0300 https://ertu.dev/posts/4_clojure-reaching-c-performance/ <p>I have a stress test written in C: 100,000 cubes flying around in space. The CPU rebuilds every cube&rsquo;s 4x4 transform matrix on every frame and sends all of them to the GPU. That is around 900,000 sine evaluations and 6 MB of matrix data per frame, and after that the GPU still has to draw 3.6 million triangles. So the frame is half CPU work, half GPU work.</p> <p>I ported it to Clojure and wanted to see how close I could get to the C version&rsquo;s FPS. I should say up front that I did not do the optimization work alone: I paired with Claude Code on it, and most of the digging in this post (the benchmarks, the JIT logs, the failed attempts) comes from that session.</p>