@spawnatmost n for i in ...

tmap(f, args...)
tmap(f, nthreads::Int, args...)
tmap1(f, args...)
tmap1(f, nthreads::Int,args...)

using ThreadTools

julia> l = SpinLock();
julia> times = [];
julia> @spawnatmost 3 for i = 1:10 # This will use only three parallel threads, even if more are avilable
            lock(l) do # We protect the access to the array using a lock
                push!(times, time())
            end
            println(i)
            sleep(1)
       end

julia> round.(diff(times), digits=2)
9-element Array{Float64,1}:
    0.0
    0.0
    1.0
    0.0
    0.0
    1.0
    0.0
    0.0
    1.0

julia> tmap(_->threadid(), 1:5) # A threaded version of map
5-element Array{Int64,1}:
 2
 6
 3
 4
 5

 julia> times = tmap(_->(t=time();sleep(0.3);t), 3, 1:10); # The second argument limits the number of threads used
 julia> round.(diff(times), digits=2)
 9-element Array{Float64,1}:
  0.0
  0.0
  0.3
  0.0
  0.0
  0.3
  0.0
  0.0
  0.3

function fib(n)
    if n <= 1 return 1 end
    return fib(n - 1) + fib(n - 2)
end

workload = fill(20, factorial(6))
times = map(1:6) do nt
    nt == 1 && return @belapsed map(fib, workload)
    @belapsed tmap(fib, $nt, workload)
end
t720 = @belapsed tmap(fib, workload)
plot(1:6, times, xlabel="Number of threads", ylabel="Time [s]")
hline!([t720], label="720 tasks", ylims=(0,Inf))

workload = fill(30, factorial(6))
times = map(1:6) do nt
    nt == 1 && return @belapsed map(fib, workload)
    @belapsed tmap(fib, $nt, workload)
end
t720 = @belapsed tmap(fib, workload)
plot(1:6, times, xlabel="Number of threads", ylabel="Time [s]")
hline!([t720], label="720 tasks", ylims=(0,Inf))