>But if I ask Python to [add up about a hundred million] [32-bit floating point numbers in the naive way], Python takes about twenty seconds anyway Really?

>But if I ask Python to [add up about a hundred million] [32-bit floating point numbers in the naive way], Python takes about twenty seconds anyway Really? $ python -m timeit -s 'import random; x = [random.random() for _ in range(100000000)]' 'sum(x)' 1 loop, best of 5: 806 msec per loop This is on 11-year-old hardware. Even the generation isn't that slow: $ time python -c 'import random; x = [random.random() for _ in range(100000000)]' real 0m10.942s user 0m9.590s sys 0m1.346s Of course, Python forces the use of doubles internally. Any optimizations inherent to 32-bit floats are simply not available.