# NAME Algorithm::HyperLogLog - Implementation of the HyperLogLog cardinality estimation algorithm # SYNOPSIS use Algorithm::HyperLogLog; my $hll = Algorithm::HyperLogLog->new(14); while(<>){ $hll->add($_); } my $cardinality = $hll->estimate(); # Estimate cardinality $hll->dump_to_file('hll_register.dump');# Dumps internal data Construct object from dumped file. use Algorithm::HyperLogLog; # Restore internal state my $hll = Algorithm::HyperLogLog->new_from_file('hll_register.dump'); # DESCRIPTION This module is implementation of the HyperLogLog algorithm. HyperLogLog is an algorithm for estimating the cardinality of a set. # METHODS ## new($b) Constructor. \`$b\` is the parameter for determining register size. (The register size is 2^$b.) \`$b\` must be a integer between 4 and 16. ## new\_from\_file($filename) This method constructs object and restore the internal data of object from dumped file(dumped by dump\_to\_file() method). ## dump\_to\_file($filename) This method dumps the internal data of an object to a file. ## add($data) Adds element to the cardinality estimator. ## estimate() Returns estimated cardinality value in floating point number. ## register\_size() Return number of register.(In the XS implementation, this equals size in bytes) ## XS() If using XS backend, this method return true value. # SEE ALSO Philippe Flajolet, Éric Fusy, Olivier Gandouet and Frédéric Meunier. HyperLogLog: the analysis of a near-optimal cardinality estimation algorithm. 2007 Conference on Analysis of Algorithms, DMTCS proc. AH, pp. 127–146, 2007. [http://algo.inria.fr/flajolet/Publications/FlFuGaMe07.pdf](http://algo.inria.fr/flajolet/Publications/FlFuGaMe07.pdf) # AUTHOR Hideaki Ohno <hide.o.j55 {at} gmail.com> # THANKS TO MurmurHash3([https://github.com/PeterScott/murmur3](https://github.com/PeterScott/murmur3)) - Austin Appleby - Peter Scott # LICENSE This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.