在线程之间发送Nalgebra VectorN

Question

我在一些单线程代码中使用了Nalgebra的VectorN<f64, N>类型，它运行良好。我现在正在尝试对算法的各个部分进行多线程处理，但在将VectorNs传递到thread::spawn调用中时遇到了问题。例如，以下代码编译失败：

use std::thread;
use nalgebra::{VectorN, DefaultAllocator, DimName};
use nalgebra::allocator::Allocator;
struct Test<N>
where
N: DimName,
DefaultAllocator: Allocator<f64, N>,
{
pub field: VectorN<f64, N>,
}
impl<N> Test<N>
where
N: DimName,
DefaultAllocator: Allocator<f64, N>,
{
pub fn test(&self) {
let handle = thread::spawn(move || {
let thing = self.field;
let thing2 = thing * 2.0;
thing2
});
let res = handle.join().unwrap();
}
}

出现此错误：

error[E0277]: `<nalgebra::base::default_allocator::DefaultAllocator as nalgebra::base::allocator::Allocator<f64, N>>::Buffer` cannot be sent between threads safely
--> trajectories/src/path/mod.rs:34:22
|
34 |         let handle = thread::spawn(move || {
|                      ^^^^^^^^^^^^^ `<nalgebra::base::default_allocator::DefaultAllocator as nalgebra::base::allocator::Allocator<f64, N>>::Buffer` cannot be sent between threads safely
|
= help: within `nalgebra::base::matrix::Matrix<f64, N, nalgebra::base::dimension::U1, <nalgebra::base::default_allocator::DefaultAllocator as nalgebra::base::allocator::Allocator<f64, N>>::Buffer>`, the trait `std::marker::Send` is not
implemented for `<nalgebra::base::default_allocator::DefaultAllocator as nalgebra::base::allocator::Allocator<f64, N>>::Buffer`
= note: required because it appears within the type `nalgebra::base::matrix::Matrix<f64, N, nalgebra::base::dimension::U1, <nalgebra::base::default_allocator::DefaultAllocator as nalgebra::base::allocator::Allocator<f64, N>>::Buffer>`
= note: required by `std::thread::spawn`

我在where子句中尝试了N和DefaultAllocator的各种定义，但还没有深入。各种各样的搜索引擎在这个问题上都没有找到任何有用的东西。

如果我用VectorN<f64, U3>(或Nalgebra中的任何其他U*类型(替换VectorN<f64, N>，则上述错误将消失。我读过Nalgebra通用编程指南，但它似乎已经过时了，也许不是我需要的；我不想要完整的泛型，只想要使用任何大小绑定的VectorN的能力。我需要在结构上设置什么特征边界，以便将field传递到线程中？

Answer 1

我在黑暗中尝试了一下(基于编译器给出的错误消息(，并通过向Allocator::Buffer添加边界来实现这一点，如下所示：

use nalgebra::allocator::Allocator;
struct Test<N>
where
N: DimName,
DefaultAllocator: Allocator<f64, N>,
<DefaultAllocator as Allocator<f64, N>>::Buffer: Send + Sync,
{
pub field: VectorN<f64, N>,
}
// snip ...

我不确定这是正确的方法，它确实会添加一些噪音，但现在它似乎让我可以将Nalgebra构造传递到线程中。