使用Arrayfire设置索引值

Question

我正在尝试用自定义值修改现有Arrayfire矩阵中的值。下面是一个将几行和几列更改为指定值(1.0(的示例。然而，我很难做到两件事：

1. 更改要更改的区域的尺寸(3x3(->(2x2(
2. 水平或垂直移动要更改的区域。我所做的任何更改似乎都给出了一个无效的索引错误

use arrayfire::{constant, Dim4, Seq, assign_seq, print};
let a    = constant(2.0 as f32, Dim4::new(&[5, 3, 1, 1]));
let b    = constant(1.0 as f32, Dim4::new(&[3, 3, 1, 1]));
let seqs = &[Seq::new(1.0, 3.0, 1.0), Seq::default()];
print(&a);
// 2.0 2.0 2.0
// 2.0 2.0 2.0
// 2.0 2.0 2.0
// 2.0 2.0 2.0
// 2.0 2.0 2.0
let sub  = assign_seq(&a, seqs, &b);

print(&sub);
// 2.0 2.0 2.0
// 1.0 1.0 1.0
// 1.0 1.0 1.0
// 1.0 1.0 1.0
// 2.0 2.0 2.0

Answer 1

经过几天的研究，我找到了图书馆的作者：

use arrayfire::{constant, Dim4, Seq, assign_seq, print};
//This is the "parent" matrix.
let a    = constant(2.0 as f32, Dim4::new(&[4, 4, 1, 1]));
//To modify a 2x2 area inside a, this must be 2x2 as well
let b    = constant(1.0 as f32, Dim4::new(&[2, 2, 1, 1]));
//Use two seq::new objects, NOTE that matrices are column major.
let seqs = &[Seq::new(1.0, 1.0, 1.0), Seq::new(1.0, 1.0, 1.0)];

Arrayfire 3.7.1还引入了一种新的优雅语法：

let mut a = arrayfire::constant(2.0 as f32, arrayfire::dim4!(4, 4));
let b = arrayfire::constant(1.0 as f32, arrayfire::dim4!(2,2));
arrayfire::print(&a);
arrayfire::eval!(a[1:1:1, 1:1:1] = b);
arrayfire::print(&a);