Compilation time regression when extending a Base method.

[KristofferC]

One of my packages (https://github.com/KristofferC/Crayons.jl) went from 0.02 seconds load time after precompilation to ~ 1 seconds from 0.5 to 0.6. I was able to reduce it to the following:

type Crayon end

begin
tic()
Base.print_with_color(crayon::Crayon, io::IO, msg::AbstractString...) =
    Base.with_output_color(print, crayon, io, msg...)
toc()
end

On 0.5:

elapsed time: 0.015108936 seconds

On 0.6:

elapsed time: 1.109898606 seconds

Removing that method, load time of package goes from 0.02s to 0.04s from 0.5 to 0.6.

[StefanKarpinski]

I'm guessing that's the #265 tax.

[KristofferC]

I don't see how this is relevant to #265? I am just adding a new method. What is different about this than extending any other method? In my view, nothing needs to be recompiled.

[yuyichao]

It's clear whether it's #265 or not but the point of the fix is that you only pay for it at method definition time (including figuring out what should trigger the recompilation during type inference) and not the runtime. It at least does spend most of the time in type inference.

[KristofferC]

I still think adding +1 second to a package load time (that's not even removed with precompilation) for a one line function that only extends a base method for a new type is unacceptable.

[vtjnash]

Oh, this is a bit confusing, since the time cost is in toc, not the method. There's definitely something wrong here:

julia> begin
       t0 = time()
       Base.print_with_color(crayon::Crayon, io::IO, msg::AbstractString) =
           nothing
       t1 = time()
       tic()
       t2 = time()
       toc()
       t3 = time()
       @show diff([t0, t1, t2, t3])
       end;
elapsed time: 0.048757574 seconds
diff([t0, t1, t2, t3]) = [0.00294709, 1.73136, 0.172295]

I don't see any reason that tic should have a back-edge from print_with_color.

[KristofferC]

It exactly the same timings when I had it in my package that did not use tic, toc. Maybe the print_with_color has a bunch of "spurious back edges" to other methods...