If I understood correctly - the Math.Abs() value would be positive roughly half the time, regardless of the steps taken to get there. That seems definitively nondeterministic.
You don’t call Math.abs() on its own, you need to give it a number. Regardless if it is positive or negative, it should always return a positive (that’s what an absolute value is). The issue here is that it was returning a negative number when given a negative value, which is wrong:
> We rerun the repro. We look at the logged value. Math.abs() is returning negative values for negative inputs. We reload and run it again. Math.abs() is returning negative values for negative inputs. We reload and run it again. Math.abs() is returning negative values for negative inputs.
Regardless, that is beside the point. I was not arguing either way if this was a deterministic bug or not, I was pointing out that the author’s conclusion does not follow from the premise. Even if the bug had turned out to be nondeterministic, they had not done the necessary steps to confidently make that assertion. There is a chasm of difference between “this bug is nondeterministic” and “I haven’t yet determined the conditions that reproduce this bug”.
My interpretation was it was replaced with the identity function (e.g. just returning the original value). But it's only replaced if the code is determined to be a hot spot. So it would work correctly until the code was in a tight loop, then it would start failing once passed a negative number.
