[jira] [Assigned] (ARROW-8598) [Rust] simd_compare_op creates buffer of incorrect length when item count is not a multiple of T::lanes()

["Paddy Horan (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-8598?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Paddy Horan reassigned ARROW-8598:
----------------------------------

    Assignee: Paddy Horan

> [Rust] simd_compare_op creates buffer of incorrect length when item count is not a multiple of T::lanes()
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: ARROW-8598
>                 URL: https://issues.apache.org/jira/browse/ARROW-8598
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Rust
>    Affects Versions: 0.17.0
>            Reporter: Yordan Pavlov
>            Assignee: Paddy Horan
>            Priority: Major
>
> the simd_compare_op function defined here [https://github.com/apache/arrow/blob/master/rust/arrow/src/compute/kernels/comparison.rs#L229]
> appears to only work correctly when item count is a multiple of T::lanes().
> Otherwise the resulting boolean array is created with a buffer of incorrect length and subsequent binary operations such as compute::and return an error.
> The no_simd_compare_op function defined in the same module does not appear to have this problem.
> This bug can be reproduced with the following code:
>  
> {code:java}
> fn main() {
>     let lanes = Int8Type::lanes();
>     println("i8 lanes: {}", lanes); // 64
>     // let item_count = 128; // this works because item_count divides by 64 (lanes) without remainder
>     let item_count = 130; // this fails because item_count divides by 64 (lanes) with remainder
>     // item_count = 130 should return error:
>     // ComputeError("Buffers must be the same size to apply Bitwise AND.")     
>     // create boolean array
>     let mut select_mask: BooleanArray = vec![true; item_count].into();
>     // create arrays with i8 values
>     let value_array: PrimitiveArray<Int8Type> = vec![1; item_count].into();
>     let filter_array: PrimitiveArray<Int8Type> = vec![2; item_count].into();
>     // compare i8 arrays and produce a boolean array
>     let result_mask = compute::gt_eq(&value_array, &filter_array).unwrap();
>     // compare boolean arrays
>      select_mask = compute::and(&select_mask, &result_mask).unwrap();
>     // print result, should be all false
>     println!("select mask: {:?}", select_mask);
> }
> {code}
>  
>  



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