[rust-dev] Reading shared immutable data

Patrick Walton pwalton at mozilla.com
Mon Dec 17 18:11:16 PST 2012

On 12/17/12 6:03 PM, Michael Neumann wrote:
> Hi,
> We have a very huge immutable data structure that we want to share
> (read-only) between many light-weight threads.
>  From what I have seen, I should use Arc. Is there any other way to
> share the data between threads?

You can also:

* Use a reader-writer lock (RWLock). This is still safe.

* Use unsafe code by casting to an unsafe pointer and sending the unsafe 
pointer over a channel; do this only as a last resort.

* Turn your shared state into a task and have other tasks access the 
data by sending it messages. This is the classical actor model solution, 
but usually ARC will be more efficient.

> And when using Arc, can I access the data in parallel by all threads?

Yes. The only synchronization cost you'll pay is the cost of an atomic 
CPU instruction whenever you send the data.


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