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Modular open-sourced Mojo this week – the language that promises the ease-of-use of Python with the performance of C++. That performance has to come from somewhere, and the compiler is where to look for it. So I read the optimiser: which passes it runs, which it pointedly does not, and what that choice suggests about where Mojo goes next.

Comparing two memory models means reading two papers and reconstructing a containment argument nobody wrote down. The Relaxed Memory Model Zoo is a map of 101 models and 145 relations where every edge states how it is known — machine-run litmus test, by construction, or cited — and a consistency gate refuses to ship a map that contradicts itself. This post covers the motivation, the evidence discipline, how the dataset was built (including where AI was used and where it was not trusted), the principles that kept it small, and how to submit corrections. A follow-up post will use the same litmus tests to locate real Rust in the lattice.

Compare-and-swap (CAS) is a central part of many implementations of lock-free algorithms synchronizing values in shared data structures. Without further scaffolding, CAS is inherently prone to the ABA problem. In this post I survey solutions mitigating ABA in the context of CAS towards a high-level classification.