bb4ea9c28b
# Objective Reduce memory usage by storing fewer copies of `FilteredAccessSet<ComponentId>`. Currently, the `System` trait exposes the `component_access_set` for the system, which is used by the multi-threaded executor to determine which systems can run concurrently. But because it is available on the trait, it needs to be stored for *every* system, even ones that are not run by the executor! In particular, it is never needed for observers, or for the inner systems in a `PipeSystem` or `CombinatorSystem`. ## Solution Instead of exposing the access from a method on `System`, return it from `System::initialize`. Since it is still needed during scheduling, store the access alongside the boxed system in the schedule. That's not quite enough for systems built using `SystemParamBuilder`s, though. Those calculate the access in `SystemParamBuilder::build`, which happens earlier than `System::initialize`. To handle those, we separate `SystemParam::init_state` into `init_state`, which creates the state value, and `init_access`, which calculates the access. This lets `System::initialize` call `init_access` on a state that was provided by the builder. An additional benefit of that separation is that it removes the need to duplicate access checks between `SystemParamBuilder::build` and `SystemParam::init_state`. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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Release Content
This directory contains drafts of documentation for the current development cycle, which will be published to the website during the next release. You can find more information in the release notes and migration guides files.