require "thread"
require "timeout"

def calc_fib(n)
if n == 0
0
elsif n == 1
1
else
calc_fib(n-1) + calc_fib(n-2)
end
end

lock = Mutex.new

threads = 20.times.collect do
Thread.new do
20.times do
begin
Timeout.timeout(0.25) do
lock.synchronize{ calc_fib(1000) }
end
rescue ThreadError => e
puts "#{e.class}: #{e.message}:\n" + e.backtrace.join("\n") + "\n\n"
rescue Timeout::Error => e
#puts e.class
nil
end
end
end
end

threads.each{ |t| t.join }