Implements the HyperLogLog and HyperLogLog++ algorithms.
HyperLogLog paper: http://algo.inria.fr/flajolet/Publications/FlFuGaMe07.pdf
HyperLogLog++ paper: http://research.google.com/pubs/pub40671.html
Documentation can be found here.
The HyperLogLog++ algorithm has much lower error for small cardinalities. This is because it uses a different representation of data for small sets of data. Data generated using this library shows the difference for N < 10000:
HyperLogLog++ also has bias correction which helps offset estimation errors in the original HyperLogLog algorithm. This correction can be seen here, again using data generated using this library: