just for the kicks i tried the new version of bytestring without -O2 and the results were even worse:

time Main1 < nums
real    0m40.092s
user    0m0.015s
sys     0m0.015s

time Main3 < nums
real    0m41.405s
user    0m0.015s
sys     0m0.015s

it got pwned even by this very naive ruby scipt (which, btw, chewed through some ~600 MB of memory ;-))

File.open("nums","r") do |f|
  puts((f.read.split.each {|x| x.to_i }).length)
end

time ruby nums.rb
real    0m21.609s
user    0m0.015s
sys     0m0.015s

so it probably can't be stressed enough: repeat "-O2"

and now seriously:

is there a reason why -O2 shouldn't be made the default (and allowing to turn off optimizations by -O0 perhaps) ?