import Foundation var array = Array(repeating: 1, count: 100000) DispatchQueue.global().async { array.insert(3, at: 99999) print("inserted") } print("start") let total = array.reduce(0) { t, c in if t % 100 == 0 { print(".", terminator: "") } return t + c } print("") print(total) print(array.count)