206af35e2b
- major refactoring to the database APIs for safer parallel processing (#78, #82): - To set an input, you now write `db.query_mut(Query).set(...)`, and you must declare your database as `mut`. - To fork a thread, you now write `db.snapshot()`, which acquires a read-lock that is only released when the snapshot is dropped (note that this read-lock blocks `set` from occuring on the main thread). - Therefore, there can only be one mutable handle to the database; all other handles are snapshots. This eliminates a variety of complex and error-prone usage patterns. - introduced the `salsa_event` callback that can be used for logging and introspection (#63) |
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| examples | ||
| src | ||
| tests | ||
| .dir-locals.el | ||
| .gitignore | ||
| .travis.yml | ||
| Cargo.toml | ||
| FAQ.md | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| README.md | ||
| rust-toolchain | ||
salsa
A generic framework for on-demand, incrementalized computation.
Obligatory warning
Very much a WORK IN PROGRESS at this point. Ready for experimental use but expect frequent breaking changes.
Credits
This system is heavily inspired by adapton, glimmer, and rustc's query system. So credit goes to Eduard-Mihai Burtescu, Matthew Hammer, Yehuda Katz, and Michael Woerister.
Key idea
The key idea of salsa is that you define your program as a set of
queries. Every query is used like function K -> V that maps from
some key of type K to a value of type V. Queries come in two basic
varieties:
- Inputs: the base inputs to your system. You can change these whenever you like.
- Functions: pure functions (no side effects) that transform your inputs into other values. The results of queries is memoized to avoid recomputing them a lot. When you make changes to the inputs, we'll figure out (fairly intelligently) when we can re-use these memoized values and when we have to recompute them.
How to use Salsa in three easy steps
Using salsa is as easy as 1, 2, 3...
- Define one or more query groups that contain the inputs and queries you will need. We'll start with one such group, but later on you can use more than one to break up your system into components (or spread your code across crates).
- Define the query functions where appropriate.
- Define the database, which contains the storage for all the inputs/queries you will be using. The query struct will contain the storage for all of the inputs/queries and may also contain anything else that your code needs (e.g., configuration data).
To see an example of this in action, check out the hello_world
example, which has a number of comments
explaining how things work. The hello_world
README has a more detailed writeup.
Salsa requires at least Rust 1.30 (beta at the time of writing).
Getting in touch
The bulk of the discussion happens in the issues and pull requests, but we have a zulip chat as well.