code: func reciprocalScale(val, n uint32) uint32 {
  	return uint32((uint64(val) * uint64(n)) >> 32)
  }
docs: // reciprocalScale scales a value into range [0, n).
  //
  // This is similar to val % n, but faster.
  // See http://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/