code: func (f PackedFormat) OverheadPerValue(bitsPerValue int) float32 {
  	switch int(f) {
  	case PACKED_SINGLE_BLOCK:
  		assert(f.IsSupported(bitsPerValue))
  		valuesPerBlock := 64 / bitsPerValue
  		overhead := 64 % bitsPerValue
  		return float32(overhead) / float32(valuesPerBlock)
  	}
  	return 0
  }
docs: /* Returns the overhead per value, in bits. */