Closes #48469 - Refactor and DRY up Kahan Sum algorithm

[JosemyDuarte]

I have created CompensatedSum to centralize the logic of Kahan Sum and replace it in all the classes mentioned by #48469.

I haven't put the looping logic inside the class since there are places where we do other stuff besides the sum in the loop, like in StatsAggregator where besides calculating the sum we also get the max and min value.

[elasticmachine]

Pinging @elastic/es-analytics-geo (:Analytics/Aggregations)

[not-napoleon]

@elasticmachine test this please

[JosemyDuarte]

Hi @not-napoleon! I just saw the build log that seems to be failing and I am not sure if I understand how my change could have caused that. If this is my fault I'm willing to solve it, but I would appreciate it if you can point me in the right direction.

Thanks!

[not-napoleon]

I like the solution overall. Left a couple of clean up comments that need to be fixed before we can merge it.

I appreciate you doing this work. In the future though, please check if someone else has already asked to work on an issue before you start on it.

[not-napoleon]

I agree, the BWC failure looks unrelated. I'll run it again after the requested changes land, and if it's green then we should be okay.

[JosemyDuarte]

Cool! Thanks for your feedback. I have a busy week, but I'll work on this before finishing the week.

[csoulios]

Just a quick note that Kahan summation is also used in #47468 for the string_stats aggregation

[not-napoleon]

@elasticmachine update branch

[not-napoleon]

@elasticmachine test this please

[not-napoleon]

Hi @JosemyDuarte

This looks good, thanks for making those changes. I'm at a conference this week, so may be slow in checking in, but I'll keep an eye on the tests. I'll let you know if there are failures I need you to look into. Not sure I'll have time to merge it this week, but if I don't, I definitely will next week.

Thanks again for the contribution!

[JosemyDuarte]

Great! Thank you for your feedback. I'll keep an eye on simple issues to keep contributing. Enjoy your conference 👍

[not-napoleon]

@elasticmachine run elasticsearch-ci/packaging-sample-matrix