Performance

How long a few programs take, what crossing threads costs, and what the compiler adds.

Here's how long a few programs take on an Apple M5 Pro:

Crossing Threads

Values cross threads about as fast as JSON would carry them, and they're read back faster. Moving 50,000 parsed JSON requests costs about 1.1 times JSON.stringify to write, and a third of JSON.parse to read. A few things keep it fast:

• Each distinct set of keys is written once per message.
• Strings that repeat within a value are written once.
• ASCII text is stored at one byte per character.

All told, 23 MB of JSON text crosses in about 7 ms.

Compiled, or With the Types Only Erased

The compiler is what makes shared structs fast. But a program also runs with its types only erased, by Node's type stripping for example. (The Vite plugin needs the compiler for now.) All it needs is the one line the compiler would add: register(import.meta.url, {main, ...}), imported from @arv/threads. That line registers the module's top-level functions, so that a thread finds the one it runs.

The checker reads the source, so it reports the same errors either way. The runtime still throws on a use after move.

Code that moves and shares plain objects runs at the same speed either way. Shared structs and SharedArrays don't. With types erased, each struct is a handle whose fields are accessors, and a SharedArray is a Proxy. That makes N-body 50 to 60 times slower:

The playground runs every program both ways (Compiled and Types erased), so you can compare them yourself.

The Prototypes has the measurements this work started from, against Porffor and plain V8.