Notices by Not Elon Musk (xy@mastodon.mit.edu)

I wrote a fast Fenwick tree library for my flash cards app: https://git.unnamed.website/sdc/tree/fenwick.c

The operation "Search for largest index with prefix sum less than or equal to s" isn't a common thing that people do with Fenwick trees so I had to read an arXiv paper about it.

The nice thing about Fenwick trees is that they're only a few lines of code but... on the other hand they use crazy incomprehensive bit hacks!

The other weird thing about the "search for largest index with prefix sum less than or equal to s" operation is that it views the Fenwick array as an implicit binary tree while the update and query ops view the array as (two different) binomial trees. So maybe the tagline for Fenwick trees should be "One array. Three trees."

I haven't done benchmarks to confirm this, but Fenwick trees should use 1/4 the memory of segtrees and be somewhat faster since they use for loops and bit hacks instead of recursion.

And here's a Fenwick the squirrel who I folded 1.5 years ago. I guess his name is because he lives in a Fenwick tree or something. When I folded him last year, I told my friends there was a squirrel in my room and they thought a real squirrel was running around wrecking havok in my room 🤣

There was an intense thunderstorm yesterday in St. Louis with 100km/h winds that *yanked a concrete slab out of the ground* (see image)

Expectedly, I lost power and exozy.me is down. It might be a few days before power returns.

Fortunately, according to the news only one person died due to the storm, but several puppies drowned in a flooded animal rescue center. 😢

My neighbor's talking about Lagrangians again

@evan @spacehobo Yeah, anyone with an mit.edu email address can create an account.

@spacehobo @evan That was true a few months ago, but I'm one of the new maintainers and we're now making sure the instance is getting plenty of love and attention again!