Consider removing `Send + Sync` requirements.

rj00a commented 5 months ago

All the data in the World currently requires Send + Sync bounds. This was done so that #4 could be implemented without a breaking change. However, I'm not sure I want this for a few reasons:

Performance: Users must use Arc and Mutex when Rc and RefCell is sufficient.
Send + Sync bounds make it difficult to work with frameworks like ggez and sdl2 that have !Send + !Sync requirements.
The multithreaded executor as currently implemented in bevy_ecs has very significant overhead, to the point where many games can improve their performance by disabling it. This may be sufficient evidence that inter-handler parallelism is not worth implementing.
Parallel iterators for Fetcher may be sufficient for most users.

I would rather not handicap this library indefinitely in order to support a feature which may not actually arrive.

spikespaz commented 5 months ago

https://github.com/kuviman/evenio/tree/non-send

andrewgazelka commented 5 months ago

I'm all for removing Send + Sync and then having a breaking change if needed. :)

I could benefit from this in https://github.com/andrewgazelka/hyperion

andrewgazelka commented 5 months ago

@spikespaz fyi non-send needs to compile with rayon feature as well

rj00a / evenio

Consider removing `Send + Sync` requirements. #36