Construct ndarray::ArrayView from multiple dimensional array

[wangjia184]

pub type SquareMatrix<T = f32> = [[T; BOARD_SIZE]; BOARD_SIZE];
pub type StateTensor<T = f32> = [SquareMatrix<T>; CHANNELS];

pub trait StateTensorExtension {
    fn shape(self: &Self) -> [usize; 3];
}
impl<T> StateTensorExtension for StateTensor<T> {
    fn shape(self: &Self) -> [usize; 3] {
        return [CHANNELS, BOARD_SIZE, BOARD_SIZE];
    }
}

I am using a quite ugly style to construct an array view from the array

    let state_tensor: StateTensor<f32> = // ...;
    let dims = state_tensor.shape();
    let x: ArrayBase<ViewRepr<&f32>, _> = unsafe {
        ArrayView::from_shape_ptr(dims, bytemuck::cast_slice(&state_tensor).as_ptr())
    };

The above code assumes multiple dimensional arrays are tightly packed in Rust. Would that work always?
What is the best way to construct ndarray::ArrayView from multiple dimensional array in my case? Or should I created a owned array instead?

[RedDocMD]

@wangjia184

The above code assumes multiple dimensional arrays are tightly packed in Rust. Would that work always?

Yes. Look at the array layout reference. It says that, essentially, arrays are always tightly packed and that they don't carry around extra meta-data. This means that multi-dimensional arrays are both tightly packed and stored in row-major order.

[H2CO3]

You shouldn't use unsafe for this! Why don't you simply use the from_shape() method of ArrayView?

let x = ArrayView::<f32, _>::from_shape(
    dims.into_dimension(),
    bytemuck::cast_slice::<_, f32>(&state_tensor)
);

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