code: func (ds *DefaultSimilarity) encodeNormValue(f float32) int64 {
  	return int64(util.FloatToByte315(f))
  }
docs: /*
  Encodes a normalization factor for storage in an index.
  
  The encoding uses a three-bit mantissa, a five-bit exponent, and the
  zero-exponent point at 15, thus representing values from around
  7x10^9 to 2x10^-9 with about one significant decimal digit of
  accuracy. Zero is also represented. Negative numbers are rounded up
  to zero. Values too large to represent are rounded down to the
  largest representable value. Positive values too small to represent
  are rounded up to the smallest positive representable value.
  */