# L-13 MCS 572 Wed 8 Feb 2023 : fibmt.jl
"""
Example from https://julialang.org/blog/2019/07/multithreading

Run typing
time JULIA_NUM_THREADS=8 julia fibmt.jl 10
at the command prompt to compute the 10-th Fibonacci number
with tasks mapped to 8 threads.
Alternatively, type
time julia -t 8 fibmt.jl 10
at the command prompt.

The recursive function fib illustrates the starting of a task
and the synchronization of the sibling task.

t = @spawn fib(n-2) starts a task to compute fib(n-2)
fetch(t) waits for t to complete and gets its return value

There can not be any speedup because of the only computation,
the '+' happens after the synchronization.
"""

import Base.Threads.@spawn

function fib(n::Int)
    if n < 2
        return n
    end
    t = @spawn fib(n-2)
    return fib(n-1) + fetch(t)
end

if length(ARGS) > 0
    nbr = parse(Int64, ARGS[1])
    println(fib(nbr))
else
    println(fib(10))
end