Performance comparison of a Vec and a boxed slice

by

In your second version, you use the type Box<&'a mut [T]>, which means there are two levels of indirection to reach a T, because both Box and & are pointers.

What you want instead is a Box<[T]>. I think the only sane way to construct such a value is from a Vec<T>, using the into_boxed_slice method. Note that the only benefit is that you lose the capacity field that a Vec would have. Unless you need to have a lot of these arrays in memory at the same time, the overhead is likely to be insignificant.

pub fn linspace_vec<'a, T: 'a>(start: T, stop: T, len: usize) -> Box<[T]>
where
    T: Float,
{
    // get 0, 1 and the increment dx as T
    let (one, zero, dx) = get_values_as_type_t::<T>(start, stop, len);
    let mut v = vec![zero; len].into_boxed_slice();
    let mut c = zero;
    let ptr: *mut T = v.as_mut_ptr();
    unsafe {
        for ii in 0..len {
            let x = ptr.offset((ii as isize));
            *x = start + c * dx;
            c = c + one;
        }
    }

    v
}

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