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Thread-safely transforming a value in a mutable map


Thread-safely transforming a value in a mutable map

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Thread-safely transforming a value in a mutable map
Tag : scala , By : Topher Cyll
Date : November 24 2020, 05:44 AM


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How to safely loop over a mutable array while modifying it?


Tag : iphone , By : user181706
Date : March 29 2020, 07:55 AM
I hope this helps . I have a controller which has an array holding actors. An actor is a object which will be called by the controller. , Create a copy of your mutable array and iterate over that.
NSArray *loopArray = [NSArray arrayWithArray: yourActorArray];
NSArray *loopArray = [yourActorArray copy];
//in this case remember to release in nonARC environment

How to safely publish mutable object from one thread to another


Tag : java , By : kangfoo2
Date : March 29 2020, 07:55 AM
should help you out Your requirement matches the Producer Consumer Pattern. Java's concurrent package a offers thread-safe collections (Like BlockingQueue etc ). Producer will create the object and put it on BlockingQueue. The Consumer then picks up the object. Here is example implementation.

Can I safely use mutable objects in RDD.aggregate in PySpark?


Tag : apache-spark , By : Shitic
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Yes, you can use mutable object as aggregation buffers for methods like fold(ByKey) or aggregate(ByKey) as it is clearly stated in the docstring:

How to safely publish a mutable object?


Tag : java , By : Jojo
Date : March 29 2020, 07:55 AM
around this issue The traditional ways:
deep copy - prevents mutations from impacting the client who is reading immutable objects - instead of copying for the client, you copy to update and the client gets an old pointer reference. customer iterator - you provide your own iterator / navigation interface, which is sensitive to a "version" field embedded with the data structure. Before visiting each element, it checks that the version has not been changed since the iterator was created (java collections does this). strong synchronization - while a reader is reading, the reader holds a lock on the data structure preventing update. Generally a bad solution, but occasionally useful (included for completeness). lazy copy - you construct an object that mostly references the original, but is triggered (as a listener) to the original, such that when a mutation is done on the original, you copy the pre-mutated value locally. This is like a lazy deep copy strategy.

What will happen in Rust if create mutable variable and mutable reference and change one of them in separate thread?


Tag : development , By : user161380
Date : March 29 2020, 07:55 AM
this one helps. Rust will not let you do unsafe things (without using the unsafe keyword), that includes anything related with threads. Why not just try and see how it fails to compile?
fn change_string(some_string: &mut String) {
    std::thread::spawn(move || {
            some_string.push_str(", World");
    });
}
error[E0621]: explicit lifetime required in the type of `some_string`
  --> src/main.rs:14:5
   |
13 | fn change_string_1(some_string: &mut String) {
   |                                 ----------- help: add explicit lifetime `'static` to the type of `some_string`: `&'static mut std::string::String`
14 |     std::thread::spawn(move || {
   |     ^^^^^^^^^^^^^^^^^^ lifetime `'static` required
fn change_string(some_string: &mut String) {
    crossbeam::scope(|s| {
        s.spawn(|_| {
            some_string.push_str(", World");
        });
    }).unwrap();
}
fn change_string(some_string: &mut String) {
    crossbeam::scope(|s| {
        s.spawn(|_| {
            some_string.push_str(", World");
        });
        s.spawn(|_| {
            some_string.push_str(", World");
        });
    }).unwrap();
}
error[E0524]: two closures require unique access to `some_string` at the same time
fn change_string(some_string: &mut String) {
    crossbeam::scope(|s| {
        s.spawn(move |_| {
            some_string.push_str(", World");
        });
        s.spawn(move |_| {
            some_string.push_str(", World");
        });
    }).unwrap();
}
error[E0382]: use of moved value: `some_string`
fn change_string(some_string: &mut String) {
    crossbeam::scope(|s| {
        s.spawn(|s| {
            some_string.push_str(", World");
            s.spawn(|_| {
                some_string.push_str(", World");
            });
        });
    }).unwrap();
}
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