add experimental @par macro to Base.Threads

Author: JeffBezanson

base/threadingconstructs.jl

@@ -1,6 +1,6 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-export threadid, nthreads, @threads
+export threadid, nthreads, @threads, @par
 
 """
     Threads.threadid()
@@ -102,3 +102,23 @@ macro threads(args...)
         throw(ArgumentError("unrecognized argument to @threads"))
     end
 end
+
+"""
+    Threads.@par expr
+
+Create and run a [`Task`](@ref) on any available thread. To wait for the task to
+finish, call [`wait`](@ref) on the result of this macro, or call [`fetch`](@ref)
+to wait and then obtain its return value.
+
+!!! compat "Julia 1.3"
+    This macro is available as of Julia 1.3.
+"""
+macro par(expr)
+    thunk = esc(:(()->($expr)))
+    quote
+        local task = Task($thunk)
+        task.sticky = false
+        schedule(task)
+        task
+    end
+end

doc/src/base/multi-threading.md

@@ -7,6 +7,7 @@ described here might (and likely will) change in the future.
 Base.Threads.threadid
 Base.Threads.nthreads
 Base.Threads.@threads
+Base.Threads.@par
 ```
 
 ```@docs

test/threads_exec.jl

@@ -647,9 +647,7 @@ function pfib(n::Int)
     if n <= 1
         return n
     end
-    t = @task pfib(n-2)
-    t.sticky = false
-    schedule(t)
+    t = @par pfib(n-2)
     return pfib(n-1) + fetch(t)::Int
 end
 @test pfib(20) == 6765