collect = true leads to a vector of nothing

[Qiaoyi-Li]

I tried the following example in Public API

@tasks for i in 1:3
       @set collect=true
       i^2
end

and it will return a length-3 vector of nothing. Note explicit return i^2 will solve this problem and gives [1, 4, 9] correctly. Is this an expected behavior or just a bug?

The julia version is

Julia Version 1.9.4
Commit 8e5136fa297 (2023-11-14 08:46 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin22.4.0)
  CPU: 12 × Apple M2 Max
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, apple-m1)
  Threads: 6 on 8 virtual cores

[MasonProtter]

Hm, that's strange, I can't reproduce:

julia> using OhMyThreads

julia> @tasks for i in 1:3
           @set collect=true
           i^2
       end
3-element Vector{Int64}:
 1
 4
 9

(@v1.10) pkg> st OhMyThreads
Status `~/.julia/environments/v1.10/Project.toml`
  [67456a42] OhMyThreads v0.5.2

Can you please show me the output of

using Pkg; pkg"which OhMyThreads"

and

@macroexpand1 @tasks for i in 1:3
     @set collect=true
     i^2
end

?

[Qiaoyi-Li]

Thanks for replying so quickly.

using Pkg; pkg"which OhMyThreads"

does not seem to be a julia command ? Maybe you mean the version? (OhMyThreads v0.5.2)

@macroexpand1 @tasks for i in 1:3
            @set collect=true
            i^2
       end
:(let
      begin
          #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:80 =#
          begin
              #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:246 =#
          end
          #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:81 =#
          begin
              #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:266 =#
          end
          #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:82 =#
          nothing
          #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:83 =#
          local function var"#4#mapping_function"(i)
                  #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:57 =#
                  #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:58 =#
                  begin
                      #= REPL[11]:2 =#
                      #= REPL[11]:3 =#
                      i ^ 2
                      #= REPL[11]:4 =#
                  end
              end
          #= /Users/qyli/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:84 =#
          OhMyThreads.tmap(var"#4#mapping_function", 1:3; )
      end
  end)

[Qiaoyi-Li]

Note additionally, I tried it with Julia v1.10.2, the result is correct.

[carstenbauer]

We can't reproduce the issue and apparently it works for you on the latest stable Julia version. For these reasons, I'm going to close this.

[MasonProtter]

Thanks for replying so quickly.

using Pkg; pkg"which OhMyThreads"

does not seem to be a julia command ? Maybe you mean the version? (OhMyThreads v0.5.2)

Yes, sorry I meant pkg"st OhMyThreads".

I just checked on v1.9.2 and 1.9.4 and and I am able to reproduce the issue. That's quite strange, I wonder what could cause it. I'm going to re-open this because we do claim support for v1.9. I'd say we should either look for a fix, or drop v1.9 support.

[MasonProtter]

Even more bizarre is that the error only occurs for me when using the macro, not if I copy-paste the macroexpanded code:

julia> @tasks for i in 1:3
           @set collect=true
           i^2
       end
3-element Vector{Nothing}:
 nothing
 nothing
 nothing

julia> @macroexpand1 @tasks for i in 1:3
           @set collect=true
           i^2
       end
:(let
      begin
          #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:80 =#
          begin
              #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:246 =#
          end
          #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:81 =#
          begin
              #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:266 =#
          end
          #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:82 =#
          nothing
          #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:83 =#
          local function var"#10#mapping_function"(i)
                  #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:57 =#
                  #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:58 =#
                  begin
                      #= REPL[18]:2 =#
                      #= REPL[18]:3 =#
                      i ^ 2
                      #= REPL[18]:4 =#
                  end
              end
          #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:84 =#
          OhMyThreads.tmap(var"#10#mapping_function", 1:3; )
      end
  end)

julia> let
             begin
                 #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:80 =#
                 begin
                     #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:246 =#
                 end
                 #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:81 =#
                 begin
                     #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:266 =#
                 end
                 #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:82 =#
                 nothing
                 #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:83 =#
                 local function var"#10#mapping_function"(i)
                         #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:57 =#
                         #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:58 =#
                         begin
                             #= REPL[18]:2 =#
                             #= REPL[18]:3 =#
                             i ^ 2
                             #= REPL[18]:4 =#
                         end
                     end
                 #= /home/mason/.julia/packages/OhMyThreads/V13wc/src/macro_impl.jl:84 =#
                 OhMyThreads.tmap(var"#10#mapping_function", 1:3; )
             end
         end
3-element Vector{Int64}:
 1
 4
 9

but I do get the wrong behaviour if I directly eval that macroexpanded code:

julia> eval(begin
           @macroexpand1 @tasks for i in 1:3
               @set collect=true
               i^2
           end
       end)
3-element Vector{Nothing}:
 nothing
 nothing
 nothing

That's really spooky. I'm starting to suspect this is a julia-side bug, but it'll require some more digging.

[carstenbauer]

Although a bit disappointing, I think we should drop 1.9 support given that 1.10 is the new LTS. (FWIW, I'm doing the same for ThreadPinning.jl in the next version.)

[MasonProtter]

Yeah lets do that.

[carstenbauer]

Support for Julia < 1.10 will be dropped in version 0.6 (to be released soon).