Protect from writing into dval if it's === val

[kshyatt]

Enzyme My doc reading ability currently has a strange issue where some objects that should be Const don't appear to be marked that way. Adding a guard here (which should be a pretty cheap check) prevents things from being overwritten until that gets fixed.

[Jutho]

So instead of being marked as Const, Enzyme makes these objects such that dval === val? Is that a valid thing to do, like, ever? That in itself seems like a much more serious issue than simply missing a constant value.

[kshyatt]

I agree, I'm trying to figure out where the problem comes from (I have a MWE) and will file an issue with Enzyme.

[kshyatt]

Here's the issue EnzymeAD/Enzyme.jl#3623

[kshyatt]

actually it's a doc issue rather than a real issue, see https://enzymead.github.io/Enzyme.jl/dev/faq/#faq-runtime-activity. So I think we'll still want this because we may need runtime activity turned on for the Enzyme equivalent of rrule_via_ad

[Jutho]

Ok, so should the check be x isa Const || (EnzymeRules.runtime_activity(config) && x.dval === x.val) as they propose in that linked issue. Or should we have our own helper function for this, as they also propose to make there:
EnzymeAD/Enzyme.jl#3597 (comment)

[kshyatt]

Ideally the fix would be to have no RA at all, which I'm trying to get set up on my PEPSKit branch. I think perhaps we should get Enzyme.jl to add the helper (I could try to add it) then just use that?

[lkdvos]

If you want it fixed already I'd probably propose already adding our own helper and then swapping it out once the upstream version is released, makes it also easier to swap out since it is a single function/signature

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
...orOperationsEnzymeExt/TensorOperationsEnzymeExt.jl	74.74% <100.00%> (ø)

... and 7 files with indirect coverage changes

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• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[kshyatt]

New is_inactive lgtm