在从 numpy 数组创建的 ndarray 切片之间执行广播添加

Question

我正在尝试编写可以从 Python 调用的 Rust 代码。为简单起见，此代码应仅采用二维布尔数组并将第二行与第一行进行异或。我尝试编写这段代码：

use numpy::PyArray2;
use pyo3::prelude::{pymodule, PyModule, PyResult, Python};

#[pymodule]
fn state_generator(_py: Python<'_>, m: &PyModule) -> PyResult<()> {
    #[pyfn(m)]
    fn random_cnots_transformation(_py: Python<'_>, x: &PyArray2<bool>) {
        let mut array = unsafe { x.as_array_mut() };
        let source = array.row(1);
        let mut target = array.row_mut(0);

        target ^= source;
    }

    Ok(())
}

但是使用

maturin

编译时会失败并出现以下错误：

error[E0271]: type mismatch resolving `<ViewRepr<&mut bool> as RawData>::Elem == ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>`
  --> src/lib.rs:35:16
   |
35 |         target ^= source;
   |                ^^ expected `bool`, found `ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>`
   |
   = note: expected type `bool`
            found struct `ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>`
   = note: required for `ArrayBase<ViewRepr<&mut bool>, Dim<[usize; 1]>>` to implement `BitXorAssign<ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>>`

error[E0277]: the trait bound `ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>: ScalarOperand` is not satisfied
  --> src/lib.rs:35:16
   |
35 |         target ^= source;
   |                ^^ the trait `ScalarOperand` is not implemented for `ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>`
   |
   = help: the following other types implement trait `ScalarOperand`:
             bool
             isize
             i8
             i16
             i32
             i64
             i128
             usize
           and 9 others
   = note: required for `ArrayBase<ViewRepr<&mut bool>, Dim<[usize; 1]>>` to implement `BitXorAssign<ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>>`

error[E0271]: type mismatch resolving `<ViewRepr<&bool> as RawData>::Elem == ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>`
  --> src/lib.rs:35:16
   |
35 |         target ^= source;
   |                ^^ expected `bool`, found `ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>`
   |
   = note: expected type `bool`
            found struct `ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>`
   = note: required for `ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>` to implement `BitXorAssign`
   = note: 1 redundant requirement hidden
   = note: required for `ArrayBase<ViewRepr<&mut bool>, Dim<[usize; 1]>>` to implement `BitXorAssign<ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>>`

error[E0277]: the trait bound `ViewRepr<&bool>: DataMut` is not satisfied
  --> src/lib.rs:35:16
   |
35 |         target ^= source;
   |                ^^ the trait `DataMut` is not implemented for `ViewRepr<&bool>`
   |
   = help: the trait `DataMut` is implemented for `ViewRepr<&'a mut A>`
   = note: required for `ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>` to implement `BitXorAssign`
   = note: 1 redundant requirement hidden
   = note: required for `ArrayBase<ViewRepr<&mut bool>, Dim<[usize; 1]>>` to implement `BitXorAssign<ArrayBase<ViewRepr<&bool>, Dim<[usize; 1]>>>`

我想这可能是因为我使用了

^=

，所以我尝试使用

+=

代替，但失败并出现以下错误：

error[E0368]: binary assignment operation `+=` cannot be applied to type `ArrayBase<ViewRepr<&mut bool>, Dim<[usize; 1]>>`
  --> src/lib.rs:35:9
   |
35 |         target += source;
   |         ------^^^^^^^^^^
   |         |
   |         cannot use `+=` on type `ArrayBase<ViewRepr<&mut bool>, Dim<[usize; 1]>>`

我已经阅读了这个答案，但我不确定这里有什么区别。如果我没记错的话，区别在于在我的代码中，

array

是一个

ArrayViewMut<bool, lx2>

，而在答案中它是一个

Array2

。

我应该在代码中更改什么来执行此类操作？

如果这很重要，我正在使用

cargo 1.72.0

，这是我的

Cargo.toml

：

[package]
name = "state_generator"
version = "0.1.0"
authors = ["Tristan NEMOZ"]
edition = "2021"

[lib]
crate-type = ["cdylib"]

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
ndarray = "0.15.6"
numpy = "0.19.0"
rand = "0.8.5"

[dependencies.pyo3]
version = "0.19.2"
features = ["extension-module"]

Answer 1

这个错误很令人困惑，但其关键在于按位异或仅使用

&ArrayView

（更准确地说，

&ArrayBase

）实现，而不是拥有的

ArrayView

，所以很简单：

target ^= &source;

但是你会面临另一个错误：

error: cannot borrow `array` as mutable because it is also borrowed as immutable
 --> src/lib.rs:5:22
  |
4 |     let source = array.row(1);
  |                  ------------ immutable borrow occurs here
5 |     let mut target = array.row_mut(0);
  |                      ^^^^^^^^^^^^^^^^ mutable borrow occurs here
6 |
7 |     target ^= &source;
  |               ------- immutable borrow later used here

这可以通过使用行上的迭代器来解决：

let mut rows = array.rows_mut().into_iter();
let mut target = rows.next().unwrap();
let source = rows.next().unwrap();

target ^= &source;