Add Statistics in KA, (only mean and var implemented)

[yolhan83]

This PR adds mean and var to KA, I also added the files for implementing the rest if you don't think it should be there don't hesitate.

PS : to implement median, we should first implement partialsort (and even multi dim partialsort), hopping the sort-pro here can do it.

[yolhan83]

note : some backend don't support f64, need to differ from Statistics in promoting integers

[yolhan83]

could we have a preffered_float(backend) ?

[yolhan83]

OneAPI 1.10 seems unrelated, var extremly slow on Metal ?

[yolhan83]

Metal perf fixed

[yolhan83]

sorry for all the commits I think its ok now

[yolhan83]

cpu var is really slow, mainly due to

for sl in eachslice(src,dims=dims)
    sl .-= selectdim(m,dims,1)
end

being slow when the dimension of the reduced dim is high.
1- Is there a better way to write it on cpu (even a kernel would be better here)
2- Is there a way to avoid it when dealing with array of more than 3 dimensions (cpu or gpu)

[yolhan83]

ok only thing missnig is nice cpu handling, gpu support any dimension now (even though feels bad to not use shared mem for this problem, we access m a lot too much)

[yolhan83]

Var still issue on CPU :

CUDA looks really nice :

[Moelf]

fix #62 I guess

[yolhan83]

yes trying to go through the CPU bad var before its ok to review

[yolhan83]

getting better

[yolhan83]

changing var alg completly to use https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Parallel_algorithm

[yolhan83]

updated benchmark :
CPU :



GPU :

[yolhan83]

ok now ready to review :)

[giordano]

Not removing the last newline character of the file (here and everywhere else) would be nice.

[yolhan83]

ah yeah

[giordano]

If you look at https://github.com/JuliaGPU/AcceleratedKernels.jl/pull/64/files you'll easily spot other files with missing ending newline (github highlights them with a special symbol). I believe vscode by default does this idiotic thing of removing the last newline, which makes very easy to guess that someone is using that editor. I hope there's an option to stop it doing stupid things.

[yolhan83]

no more symbols, I also removed non implemented statistics files for now, we will add them as they are implemented I think