code: func minRun(length int) int {
  	assert2(length >= MINRUN, fmt.Sprintf("length=%v", length))
  	n := length
  	r := 0
  	for n >= 64 {
  		r = (r | (n & 1))
  		n = int(uint(n) >> 1)
  	}
  	minRun := n + r
  	assert(minRun >= MINRUN && minRun <= RUN_THRESHOLD)
  	return minRun
  }
docs: // Minimum run length for an array of given length.