Par_iter_mut with Rc

help
1

The following code doesn't compile when the struct contains a reference counter, and works otherwise. I understand that a trait is not satisfied for Rc<T>, but how can I specify it properly?

use rayon::prelude::*;
use std::rc::Rc;
pub trait E: Clone + Send {
    fn eval(&self) -> f64;
}
struct C<T: E> {
//  d: T,
    d: Rc<T>,
    v: f64,
}
type P<T> = Vec<C<T>>;
fn eval_pop<T: E>(mut p: P<T>) -> P<T> {
	p.par_iter_mut().for_each(|v| {v.v = v.d.eval()});
    return p;
}
2

If something reference-counted must be accessible from mulltiple threads (such as inside parallel iteration), it have to be Arc, not Rc.

3

Doesn't compile either with Rc or Arc

4

You will need to add Send + Sync bounds to T as well.

use rayon::prelude::*;
use std::sync::Arc;
pub trait E: Clone + Send {
    fn eval(&self) -> f64;
}
struct C<T: E> {
//  d: T,
    d: Arc<T>,
    v: f64,
}
type P<T> = Vec<C<T>>;
fn eval_pop<T: E + Send + Sync>(mut p: P<T>) -> P<T> {
	p.par_iter_mut().for_each(|v| {v.v = v.d.eval()});
    return p;
}

Unfortunately the error message here, as long as those were missing, was not all that helpful.

5

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