Change threading API

[chriselrod]

This issue goes for Gaius as well. I really don't like the precompile-time decision for whether or not to use threads.

[chriselrod]

I use a bash script to update and precompile Julia package (i.e., git pulls my deved libraries, and then calls julia --startup=no -e 'using Pkg; Pkg.update()'), and I don't really want to add a -tauto to that script just to use threaded Octavian/Gaius.

[DilumAluthge]

Hmmm. Are you sure that the decision to thread is locked in at precompile time?

$ julia -t 1
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.7.0-DEV.191 (2020-12-29)
 _/ |\__'_|_|_|\__'_|  |  Commit ad7e59a6b1 (3 days old master)
|__/                   |

julia> using Octavian

julia> @macroexpand(Octavian.@_spawn(1 + 1))
:(1 + 1)

julia> Threads.nthreads()
1

julia>
$ julia -t 4
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.7.0-DEV.191 (2020-12-29)
 _/ |\__'_|_|_|\__'_|  |  Commit ad7e59a6b1 (3 days old master)
|__/                   |

julia> using Octavian

julia> @macroexpand(Octavian.@_spawn(1 + 1))
quote
    #= threadingconstructs.jl:172 =#
    let
        #= threadingconstructs.jl:173 =#
        local var"#1#task" = Base.Threads.Task((()->begin
                            #= threadingconstructs.jl:169 =#
                            1 + 1
                        end))
        #= threadingconstructs.jl:174 =#
        (var"#1#task").sticky = false
        #= threadingconstructs.jl:175 =#
        if $(Expr(:islocal, Symbol("##sync#41")))
            #= threadingconstructs.jl:176 =#
            Base.Threads.put!(var"##sync#41", var"#1#task")
        end
        #= threadingconstructs.jl:178 =#
        Base.Threads.schedule(var"#1#task")
        #= threadingconstructs.jl:179 =#
        var"#1#task"
    end
end

julia> Threads.nthreads()
4

julia>
$ julia -t 1
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.7.0-DEV.191 (2020-12-29)
 _/ |\__'_|_|_|\__'_|  |  Commit ad7e59a6b1 (3 days old master)
|__/                   |

julia> using Octavian

julia> @macroexpand(Octavian.@_spawn(1 + 1))
:(1 + 1)

julia> Threads.nthreads()
1

julia>
$ julia -t 4
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.7.0-DEV.191 (2020-12-29)
 _/ |\__'_|_|_|\__'_|  |  Commit ad7e59a6b1 (3 days old master)
|__/                   |

julia> using Octavian

julia> @macroexpand(Octavian.@_spawn(1 + 1))
quote
    #= threadingconstructs.jl:172 =#
    let
        #= threadingconstructs.jl:173 =#
        local var"#1#task" = Base.Threads.Task((()->begin
                            #= threadingconstructs.jl:169 =#
                            1 + 1
                        end))
        #= threadingconstructs.jl:174 =#
        (var"#1#task").sticky = false
        #= threadingconstructs.jl:175 =#
        if $(Expr(:islocal, Symbol("##sync#41")))
            #= threadingconstructs.jl:176 =#
            Base.Threads.put!(var"##sync#41", var"#1#task")
        end
        #= threadingconstructs.jl:178 =#
        Base.Threads.schedule(var"#1#task")
        #= threadingconstructs.jl:179 =#
        var"#1#task"
    end
end

julia> Threads.nthreads()
4

[DilumAluthge]

Oh I see. At precompile time, we will call @_spawn while defining various functions inside Octavian. And then those functions will be locked to thread or not-thread based on the value of Threads.nthreads() in the precompilation process at precompile time.

[chriselrod]

Yeah. The API is my fault, because I didn't realize that when I first defined the macro.