Fibonacci numbers in Crystal - concurrent and non-concurrent

fibonacci.cr

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

######################################################
# Concurrent version:
# $: crystal build --release fibonacci.cr
# $: time ./fibonacci
# 701408732
# 
# real    0m2.591s
# user    0m2.584s
# sys     0m0.006s
# channel = Channel(Int32).new
# sum = 0
# (1..42).each do |i|
#   spawn do
#     channel.send(fib(i))
#   end
#   sum += channel.receive
# end
# puts sum

######################################################
# Non-concurrent version:
# $: crystal build --release fibonacci.cr
# $: time ./fibonacci
# 701408732
# 
# real    0m2.694s
# user    0m2.688s
# sys     0m0.005s
sum = 0
(1..42).each do |i|
  sum += fib(i)
end
puts sum