Plurrrr

I’ve had the pleasure of having had to analyse multi-gigabyte JSON dumps in a project context recently. JSON itself is actually a rather pleasant format to consume, as it’s human-readable and there is a lot of tooling available for it. JQ allows expressing sophisticated processing steps in a single command line, and Jupyter with Python and Pandas allow easy interactive analysis to quickly find what you’re looking for.

Daniel Lemire's recent post "runtime asserts are not free" looks at the run-time cost of assert statements in C and shows that a simple assert in a frequently executed loop can cause significant overhead.

My own opinion on assertions has shifted over the years, from "I don't see the point" to "use them sparingly" to "use them as much as possible". That last shift is largely due to Rust having two kinds of "assert" statement – assert and debug_assert – which has allowed me to accurately express two different kinds of assertions, largely freeing me from performance worries. If you come from a language that only has one kind of assert statement, this distinction can seem pointless, so in this post I want to briefly explain why it helped shift my thinking.

Very often during development, it is useful to run your code in a scenario that is as near to a final deployment as possible, but not in some cloud environment where it’s hard to change specific parts without going through the full CI/CD chain. I find it very useful to quickly build, run, iterate, rebuild, and rerun VMs with NixOS Linux on my development machines. This week I demonstrate this aspect of my workflow with NixOS.