---
name: "Algorithm::HyperLogLog"
section: "3pm"
platform: "linux"
package: "libalgorithm-hyperloglog-perl"
version: "0.24-2+b3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Algorithm::HyperLogLog"
---

# Algorithm::HyperLogLog(3pm)

Implementation of the HyperLogLog cardinality estimation algorithm

## 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, 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\>

## 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.