code: func (h *HLLPP) Add(v []byte) {
  	x := murmurSum64(v)
  
  	if h.sparse {
  		h.tmpSet = append(h.tmpSet, h.encodeHash(x))
  
  		// is tmpSet >= 1/4 of memory limit?
  		if 4*uint32(len(h.tmpSet))*8 >= 6*h.m/4 {
  			h.flushTmpSet()
  		}
  	} else {
  		idx := uint32(sliceBits64(x, 63, 64-h.p))
  		rho := rho(x<<h.p | 1<<(h.p-1))
  		h.updateRegisterIfBigger(idx, rho)
  	}
  }
docs: // Add will hash v and add the result to the HyperLogLog++ estimator h. hllpp
  // uses a built-in non-streaming implementation of murmur3.