_max = 1000000000
_size = _max/16 + 16
uint8 primes(_size)

local fn twins( max as uint64 )
  CFTimeInterval t : t = fn CACurrentMediaTime
  uint64 num, p, twins = 0, prev = 0

  for num = 3 to max step 2
    if primes(num >> 4) & bit((num & 15) >> 1) then continue

    p = num * num
    while p < max
      primes(p >> 4) |= bit((p & 15) >> 1)
      p += num << 1
    wend

    twins += (num == prev + 2)
    prev   = num
  next

  printf @"%10d twin primes in first %d integers   %.3f ms."¬
  , twins, max, 1000 * (fn CACurrentMediaTime - t)
end fn

window 1, @"Twin Primes"
print
CFTimeInterval tm : tm = fn CACurrentMediaTime
for byte x = 1 to 9
  fn memset( @primes(0), 0, _size ) //Clear array for each run
  fn twins( 10^x )
next
printf @"  Total time: %.3f sec.",(fn CACurrentMediaTime - tm)

handleevents