How to effectively use ArrayView?

help
1

Hi All,

From this community I have learnt a lot. Now I have a new problem. I have a function which is like below,

fn test( struct1: &MyStruct, struct2: &MyStruct2) -> ArrayView1<f32> {
    let arr2: Array2 = struct1.arr;

   let res = match struct2.method {
        1 => fn1(&arr2, struct2.n); //Returns ArrayView1 by doing arr2.column(n)
        _ => fn2(&arr); //Returns Array1 by doing arr2.column(0) + arr2.column(1)
   }

   return res;
}

fn start(struct1: &mut MyStruct, struct2: &mut MyStruct2) {
    let arr = test(&struct1, &struct2);
    let res = test2(arr);
}

Because of different return types, the match throws error. I also tried fn(&arr).view() but rust complains temp variable lost. I can convert ArrayView1 to Array1 in fn1 but I dont want to because I am working on a very huge array 15000 * 1500 and it might be a hit in performance. Also this test function is called 1000 times. So I am looking for an optimised solution.

I think there is something I should do with lifetime. But I didn't learn it yet and felt it is advanced programming

2

I'm assuming you are talking about the ndarray ArrayView and Array types here. In this case you could use the Cow version of those to represent either an owned array or a view into an array: ndarray::CowArray

3

Yes you are right. I am using ndarray. Sorry for missing that important detail

4

Thanks. Finally I figured out how to use the CowArray :slight_smile:

fn use_cow<'a>(input1: &'a input) -> CowArray<'a, f32, Ix1> {
    let arr = // Some function which returns Array or ArrayView
    return CowArray::from(arr);
}

Replace Ix1 with the required dimension.

5

This topic was automatically closed 90 days after the last reply. We invite you to open a new topic if you have further questions or comments.