slotmap v0.0.4

Slotmap in Typescript

This was an experiment to see about building something like a multi-value SlotMap as the basis for an Entity Component System in Javascript/Typescript (just for experimental purposes)

It stops short of many things that would be required to tie them together, since I first wanted to see if aligning things with Arrays gave a performance boost (without relying on an unrealistic API).

See Results below :)

In terms of speed - the top priority is iteration over values. Less priority is given to insertion/removal

In terms of features - insert() gives a unique key (within the given slotmap) and can be used for lookups with zero conflicts (until the "generation/version" wraps... but that's a story for another time and isn't relevant to the test here)

There are API's for updating and getting in any order and iterating over the values and/or keys, as well as selectively culling the values to get only what's needed.

Basically - things can be thought of as a structure of arrays, or an array of structures, or a map of structures, and the API supports all of those (just like you can iterate over a native Map's values and destructure objects, or keys or do a lookup by key, but here we're storing things in arrays - and only Arrays + TypedArays, no objects or hashmaps anywhere!).

The maximum number of live keys it can hold is currently around 1MM.

Errors and missing values are expressed with fp-ts, so that's a peer dependency

Inspired by beach_map and EnTT

(but doesn't go near as far as either of those in terms of features or performance)

Results

Success!

When the values are iterated like an ECS, it's significantly better, like 2x better

When the slotmap is treated like a regular map, it's pretty much equal (actually it's faster - but not by as wide a margin)

100 entries:

running benchmark for 100 entries

nativemap keys x 5,015 ops/sec ±0.38% (95 runs sampled)
slotmap keys x 6,182 ops/sec ±1.15% (92 runs sampled)
nativemap values x 6,131 ops/sec ±1.90% (93 runs sampled)
slotmap values x 10,448 ops/sec ±0.87% (90 runs sampled)

Fastest is slotmap values

1000 entries:

nativemap keys x 397 ops/sec ±2.75% (87 runs sampled)
slotmap keys x 539 ops/sec ±0.74% (93 runs sampled)
nativemap values x 599 ops/sec ±0.46% (91 runs sampled)
slotmap values x 1,021 ops/sec ±3.11% (89 runs sampled)

Fastest is slotmap values

Usage

The benchmark has examples, as well as tests - and source has the interface defined at the top of slotmap.ts :)

If you want to use the lib, for whatever reason, it is published to npm under slotmap

TODO

This could be taken to the next level for a proper ECS with a few changes:

1. Solve the problem of version expiring when add/remove in a tight loop (use beach_map approach instead of EnTT)
2. Have different slotmaps indexed by the same keys
3. Ability to add/remove the components, not the entire entry (e.g. by adding/removing on those different slotmaps)