Algorithm::HyperLogLog

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.

merge($other)

Merges the estimate from 'other' into this object, returning the estimate of their union.

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, Eric Fusy, Olivier Gandouet and Frederic Meunier. HyperLogLog: the analysis of a near-optimal cardinality estimation algorithm. 2007 Conference on Analysis of Algorithms, DMTCS proc. AH, pp. 127X146, 2007. <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>)

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.