rust - 使用 Box 分配大型数组时，线程 '' 已溢出其堆栈

Question

我正在实现 combsort .我想在堆栈上创建固定大小的数组，但它显示堆栈溢出。当我将它更改为在堆上时(Rust by Example 说 to allocate in the heap we must use Box )，它仍然显示 stack overflow。

fn new_gap(gap: usize) -> usize {
    let ngap = ((gap as f64) / 1.3) as usize;
    if ngap == 9 || ngap == 10 {
        return 11;
    }
    if ngap < 1 {
        return 1;
    }
    return ngap;
}

fn comb_sort(a: &mut Box<[f64]>) {
    // previously: [f64]
    let xlen = a.len();
    let mut gap = xlen;
    let mut swapped: bool;
    let mut temp: f64;
    loop {
        swapped = false;
        gap = new_gap(gap);
        for i in 0..(xlen - gap) {
            if a[i] > a[i + gap] {
                swapped = true;
                temp = a[i];
                a[i] = a[i + gap];
                a[i + gap] = temp;
            }
        }
        if !(gap > 1 || swapped) {
            break;
        }
    }
}

const N: usize = 10000000;

fn main() {
    let mut arr: Box<[f64]> = Box::new([0.0; N]); // previously: [f64; N] = [0.0; N];
    for z in 0..(N) {
        arr[z] = (N - z) as f64;
    }
    comb_sort(&mut arr);
    for z in 1..(N) {
        if arr[z] < arr[z - 1] {
            print!("!")
        }
    }
}

输出:

thread '<main>' has overflowed its stack
Illegal instruction (core dumped)

或者

thread 'main' has overflowed its stack
fatal runtime error: stack overflow

我知道我的stack size不够用，和C++在函数内部创建非堆数组的时候一样太大了，但是这段代码是用了heap但是还是显示stack overflow。这段代码到底有什么问题？

Answer 1

据我所知，代码似乎仍在尝试先在堆栈上分配数组，然后再将其移入框中。

如果我切换到 Vec<f64>，它对我有用代替 Box<[f64]>像这样:

fn new_gap(gap: usize) -> usize {
    let ngap = ((gap as f64) / 1.3) as usize;
    if ngap == 9 || ngap == 10 {
        return 11;
    }
    if ngap < 1 {
        return 1;
    }
    return ngap;
}

fn comb_sort(a: &mut [f64]) {
    // previously: [f64]
    let xlen = a.len();
    let mut gap = xlen;
    let mut swapped: bool;
    let mut temp: f64;
    loop {
        swapped = false;
        gap = new_gap(gap);
        for i in 0..(xlen - gap) {
            if a[i] > a[i + gap] {
                swapped = true;
                temp = a[i];
                a[i] = a[i + gap];
                a[i + gap] = temp;
            }
        }
        if !(gap > 1 || swapped) {
            break;
        }
    }
}

const N: usize = 10000000;

fn main() {
    let mut arr: Vec<f64> = std::iter::repeat(0.0).take(N).collect();
    //let mut arr: Box<[f64]> = Box::new([0.0; N]); // previously: [f64; N] = [0.0; N];
    for z in 0..(N) {
        arr[z] = (N - z) as f64;
    }
    comb_sort(arr.as_mut_slice());
    for z in 1..(N) {
        if arr[z] < arr[z - 1] {
            print!("!")
        }
    }
}