[wormlord]

I implemented a toy market ledger in Rust. I initially thought to use a B-Tree because that's the conventional wisdom right? It was sooooo slow. Running valgrind showed that 99.5% of the time was spent doing memory allocation and traversing pointers.

A hashmap of vectors was so stupidly fast. If you keep them sorted each insertion is dirt cheap, and binary search is dirt cheap.

[grovesNL]

Do you mean time was used as the key for the hashmap? What was the vector used for in that setup?

[wormlord]

Vectors contain buy/sell orders and are sorted by price, the keys of the hashmap were different securities. Buy orders and sell orders lived in separate vectors