bloom-filter.el

An implementation of Bloom filters in elisp.

A Bloom filter is a space efficient, probabilistic data structure that is used to test if an element is a member of a set. False positive are possible, false negatives are not.

Version 0.1.0 Tested with emacs 24.

Installation

Copy bloom-filter.el in a directory in load-path

Functions

make-bloom-filter
bloom-filter-add
bloom-filter-query
list-to-bloom-filter
bloom-filters-union
bloom-filters-intersection
bloom-filter-p
bloom-filter-size
bloom-filter-hash-funs-num
bloom-filter-vector

Usage example

(require 'bloom-filter)

(setq bf (make-bloom-filter 512 4))

(bloom-filter-add "test" bf)
(bloom-filter-query "test" bf) ;; ==> t
(bloom-filter-query "toast" bf) ;; ==> nil

(setq bf1 (list-to-bloom-filter '(rose lily daisy) 512 4))
(bloom-filter-query 'rose bf1) ;; ==> t
(bloom-filter-query 'violet bf1) ;; ==> nil

(setq bf2 (list-to-bloom-filter '(daisy peach mario luigi) 512 4))
(bloom-filter-query 'rose (bloom-filters-union bf1 bf2)) ;; ==> t
(bloom-filter-query 'daisy (bloom-filters-union bf1 bf2)) ;; ==> t
(bloom-filter-query 'mario (bloom-filters-union bf1 bf2)) ;; ==> t
(bloom-filter-query 'violet (bloom-filters-union bf1 bf2)) ;; ==> nil

(bloom-filter-query 'daisy (bloom-filters-intersection bf1 bf2)) ;; ==> t
(bloom-filter-query 'mario (bloom-filters-intersection bf1 bf2)) ;; ==> nil
(bloom-filter-query 'rose (bloom-filters-intersection bf1 bf2)) ;; ==> nil

Addition informations on Bloom filters

Wikipedia

TODO

Find a better internal representation (now it's a tagged vector)
Remove dependency on 'cl
Move tests to a separate file
Better test coverage
Test compatibility with other versions of emacs
More speed!

Author

Giampaolo Guiducci giampaolo.guiducci@gmail.com

License

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

gosub / bloom-filter.el