Question

the code below outputs 0.0. is this because of the overflow? how to avoid it? if not, why?

p ((1..100000).map {rand}).reduce :*

I was hoping to speed up this code:

p r.reduce(0) {|m, v| m + (Math.log10 v)}

and use this instead:

p Math.log10 (r.reduce :*)

but apparently this is not always possible…

Answer 1

The values produced by rand are all between 0.0 and 1.0. This means that on each multiplication, your number gets smaller. So by the time you have multiplied 1000 of them, it is probably indistinguishable from 0.

At some point, ruby will take your number to be so small that it is 0. for instance: 2.0e-1000 # => 0