Simulating Infinity in Conway's Game of Life with Modern C++

https://ryanjk5.github.io/posts/GOLDE/

Comments

ofrzetaMay 21, 2026, 9:42 AM
"I had heard the rumors that C++ was a scary language filled with footguns and segmentation faults, but I had never given it a fair chance myself" - props for this. There's too much hearsay in software engineering.
fc417fc802May 21, 2026, 10:14 AM
And then immediately afterwards we see const T* in a supposedly immutable data structure meaning the pointer remains mutable. Yet another classic footgun.
mooreatMay 21, 2026, 11:32 AM
It looked to me like most of the raw pointers in the blog were const. Sometimes you don't want the baggage of smart pointers and getting a cheap easily copyable view of your data is nice, so you want to return a const T. Usually if an API returns a const T I assume lifetimes are handled for me and that the ptr is valid as long as it is not nullptr.
fc417fc802May 21, 2026, 11:56 PM
I just double checked and don't see any const pointers, only mutable pointers to const data.
epsMay 21, 2026, 9:04 AM
Small nit, this - https://ryanjk5.github.io/assets/2026-05-14-GOLDE/torus.gif - is not what's conventionally referred to as a torus in CGoL. In torus left and right edges are also connected.
xeyowntMay 21, 2026, 9:51 AM
Yes, it's more an infinite cylinder.
jdw64May 21, 2026, 6:41 AM
It seems like the thread_local CacheIndex only determines which cache to use, but it doesn't actually guarantee thread safety for concurrent access to the HashLifeCache itself. What would be a good solution for this?

Should I use a mutex for each cache instance? As a beginner developer, my guess is that the original author assumes data races won't occur based on the execution timing. However, I'm really not sure if that assumption is actually correct/safe.

nnevatieMay 21, 2026, 11:06 AM
In my view, thread_local is a bit of a code/design red flag. I didn't read the entire code in this case to see whether the thread_local use is warranted or not, though.
gpderettaMay 21, 2026, 12:04 PM
a thread_local is just a global variable. Mutable global variables are of course bad, but in this case the threadindex is immutable once created, so it is perfectly fine.
nnevatieMay 21, 2026, 12:45 PM
Yes, technically it is of course fine, just as a design I find use of thread_local is more of an afterthought than something I'd prefer.
hiroakiaizawaMay 21, 2026, 9:02 AM
Interesting approach. I like that the implementation focuses on scalability rather than only visualization.
HarHarVeryFunnyMay 21, 2026, 2:31 PM
It's extremely inefficient, using pointers to neighboring cells.

If you want to handle the grid edges (whether for a wrap-around "infinite" grid, or not) without too much special code, then leave a 1-cell border around the grid and fill this with the appropriate data (empty cells, or wraparound cells). If you really want to be efficient then just write the special-case edge code.

classifiedMay 21, 2026, 7:45 AM
Fricking cool, I love it.
ontouchstartMay 21, 2026, 11:33 AM
This would be a cool template project to learn C++ without the pollution of LLM slop.