a = []
100000.times { a << 1 }

t1 = Thread.new do
  loop { p a.to_s.length; sleep 0.5 }
end

t2 = Thread.new do
  loop {
    a.clear;
    sleep 0.01
    100000.times { a << 1 }
    sleep 0.01
  }
end

t3 = Thread.new do
  loop {
    a.clear;
    sleep 0.01
    100000.times { a << 1 }
    sleep 0.01
  }
end

t1.join
t2.join
t3.join