When Parallel: Pull, Don't Push
This article was discussed on Hacker News. I’ve noticed a small pattern across a few of my projects where I had vectorized and parallelized some code. The original algorithm had a “push” approach, the optimized version instead took a “pull” approach. In this article I’ll describe what I mean, though it’s mostly just so I can show off some pretty videos, pictures, and demos. Sandpiles A good place
Go's Tooling is an Undervalued Technology
This article was discussed on Hacker News, on reddit, and on Lobsters. Regardless of your opinions of the Go programming language, the primary implementation of Go, gc, is an incredible piece of software engineering. Everyone ought to be blown away by it! Yet not only is it undervalued in general, even the Go community itself doesn’t fully appreciate it. It’s not perfect, but it has unique feature
Go Slices are Fat Pointers
This article was discussed on Hacker News. One of the frequent challenges in C is that pointers are nothing but a memory address. A callee who is passed a pointer doesn’t truly know anything other than the type of object being pointed at, which says some things about alignment and how that pointer can be used… maybe. If it’s a pointer to void (void *) then not even that much is known. The number o
Endlessh: an SSH Tarpit
This article was discussed on Hacker News (later), on reddit (also), featured in BSD Now 294. Also check out this Endlessh analysis. I’m a big fan of tarpits: a network service that intentionally inserts delays in its protocol, slowing down clients by forcing them to wait. This arrests the speed at which a bad actor can attack or probe the host system, and it ties up some of the attacker’s resourc
The CPython Bytecode Compiler is Dumb
This article was discussed on Hacker News. Due to sheer coincidence of several unrelated tasks converging on Python at work, I recently needed to brush up on my Python skills. So far for me, Python has been little more than a fancy extension language for BeautifulSoup, though I also used it to participate in the recent tradition of writing one’s own static site generator, in this case for my wife’
Minimalist C Libraries
In the past year I’ve written a number of minimalist C libraries, particularly header libraries. The distinction for “minimalist” is, of course, completely arbitrary and subjective. My definition in this context isn’t about the library’s functionality being stupidly trivial or even necessarily simple. I’m talking about interface (API) complexity and the library’s run time requirements. Complex fun
When FFI Function Calls Beat Native C
Update: There’s a good discussion on Hacker News. Over on GitHub, David Yu has an interesting performance benchmark for function calls of various Foreign Function Interfaces (FFI): https://github.com/dyu/ffi-overhead He created a shared object (.so) file containing a single, simple C function. Then for each FFI he wrote a bit of code to call this function many times, measuring how long it took. Fo
Emacs 26 Brings Generators and Threads
Emacs 26.1 was recently released. As you would expect from a major release, it comes with lots of new goodies. Being a bit of an Emacs Lisp enthusiast, the two most interesting new features are generators (iter) and native threads (thread). Correction: Generators were actually introduced in Emacs 25.1 (Sept. 2016), not Emacs 26.1. Doh! Update: ThreadSanitizer (TSan) quickly shows that Emacs’ threa
When the Compiler Bites
Update: There are discussions on Reddit and on Hacker News. So far this year I’ve been bitten three times by compiler edge cases in GCC and Clang, each time catching me totally by surprise. Two were caused by historical artifacts, where an ambiguous specification lead to diverging implementations. The third was a compiler optimization being far more clever than I expected, behaving almost like an
A Tutorial on Portable Makefiles
In my first decade writing Makefiles, I developed the bad habit of liberally using GNU Make’s extensions. I didn’t know the line between GNU Make and the portable features guaranteed by POSIX. Usually it didn’t matter much, but it would become an annoyance when building on non-Linux systems, such as on the various BSDs. I’d have to specifically install GNU Make, then remember to invoke it (i.e. as
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Netpbm Animation Showcase
Chunking Optimizations: Let the Knife Do the Work
Legitimate Use of Variable Length Arrays
UTF-8 String Indexing Strategies
The Day I Fell in Love with Fuzzing
Intercepting and Emulating Linux System Calls with Ptrace
Debugging Emacs or: How I Learned to Stop Worrying and Love DTrace
Stack Clashing for Fun and Profit
Some Performance Advantages of Lexical Scope
Baking Data with Serialization