Compile error using `dot` on slices of 3D arrays about chapel

[Guillaume-Helbecque]

Hello, I'm not a Chapel expert but I think I could help you to workaround this issue.

In my understanding, dot calls the private _matmatMult method, itself calling hasNonStridedIndices(Adom). The compiler error you get is due to a mismatch in hasNonStridedIndices argument (Adom). It must be a domain(2), but matA[1, .., ..].domain.type is an ArrayViewRankChangeDom (due to an internal conversion I guess).

One workaround that could help you is to use temporary variables/constants and explicitly specify their domain (otherwise it is assigned to ArrayViewRankChangeDom also):

use LinearAlgebra;

var matA : [1..3, 1..3, 1..3] real;
var matB : [1..3, 1..3, 1..3] real;

const matC : [1..3, 1..3] real = matA[1, .., ..];
const matD : [1..3, 1..3] real = matB[1, .., ..];

writeln(dot(matC, matD));

Note for potential fix: One solution could be to check the type of Adom in hasNonStridedIndices, and if not domain(2), perform the explicit cast ArrayViewRankChangeDom:domain(2).

[bradcray]

@redhatturtle : Thanks for filing this, and sorry for the lack of responses from the Chapel dev team until now. We were working on getting 1.32 release notes out the door and fell behind on user issues a bit as a result. And thanks to @Guillaume-Helbecque for helping out while we were distracted.

I've got a modest fix to the hasNonStridedIndices() utility being used in this code path to make it rank-neutral, which seems as though it gets the cases in the OP working as expected, and I believe should enable other cases as well (such as multiplying rank-preserving slice operations). I do need to do more testing on it still before merging, but if you want to give it a look and see whether it works for you, I'd be curious for any feedback: #23737

[bradcray]

@redhatturtle : Just noting that this has now been merged. Thanks again for reporting it, and please let me know if it does not resolve the original problem in your own code (rather than just this reproducer).