NAME
LCS::BV - Bit Vector (BV) implementation of the Longest Common
Subsequence (LCS) Algorithm
SYNOPSIS
use LCS::BV;
$object = LCS::BV->new;
@lcs = $object->LCS(\@a,\@b);
$llcs = $object->LLCS(\@a,\@b);
$positions = $object->prepare(\@a);
$llcs = $object->LLCS_prepared($positions,\@b);
ABSTRACT
LCS::BV implements Algorithm::Diff using bit vectors and is faster in
most cases, especially on strings with a length shorter than the used
wordsize of the hardware (32 or 64 bits).
DESCRIPTION
CONSTRUCTOR
new()
Creates a new object which maintains internal storage areas for the
LCS computation. Use one of these per concurrent LCS() call.
METHODS
LLCS(\@a,\@b)
Return the length of a Longest Common Subsequence, taking two
arrayrefs as method arguments. It returns an integer.
LCS(\@a,\@b)
Finds a Longest Common Subsequence, taking two arrayrefs as method
arguments. It returns an array reference of corresponding indices,
which are represented by 2-element array refs.
prepare(\@a)
For comparison of the same sequence @a many times against different
sequences @b it can be faster to prepare @a. It returns a hashref of
positions. This works only on object mode.
LLCS_prepared($positions,\@b)
Return the length of a Longest Common Subsequence, with one side
prepared. It returns an integer. It is two times faster than LLCS().
EXPORT
None by design.
STABILITY
Until release of version 1.00 the included methods, names of methods
and their interfaces are subject to change.
Beginning with version 1.00 the specification will be stable, i.e. not
changed between major versions.
REFERENCES
H. Hyyroe. A Note on Bit-Parallel Alignment Computation. In M. Simanek
and J. Holub, editors, Stringology, pages 79-87. Department of Computer
Science and Engineering, Faculty of Electrical Engineering, Czech
Technical University, 2004.
SPEED COMPARISON
Intel Core i7-4770HQ Processor
Intel® SSE4.1, Intel® SSE4.2, Intel® AVX2
4 Cores, 8 Threads
2.20 - 3.40 GHz
6 MB Cache
16 GB DDR3 RAM
LCS-BV/xt$ perl 50_diff_bench.t
LCS: Algorithm::Diff, Algorithm::Diff::XS, LCS, LCS::BV
LCS: [Chrerrplzon] [Choerephon]
Rate LCS:LCS AD:LCSidx AD:XS:LCSidx LCS:BV:LCS
LCS:LCS 9225/s -- -72% -87% -88%
AD:LCSidx 33185/s 260% -- -53% -58%
AD:XS:LCSidx 70447/s 664% 112% -- -12%
LCS:BV:LCS 79644/s 763% 140% 13% --
LCS: [qw/a b d/ x 50], [qw/b a d c/ x 50]
Rate LCS:LCS AD:LCSidx LCS:BV:LCS AD:XS:LCSidx
LCS:LCS 49.5/s -- -37% -96% -99%
AD:LCSidx 79.0/s 60% -- -94% -98%
LCS:BV:LCS 1255/s 2434% 1488% -- -69%
AD:XS:LCSidx 4073/s 8124% 5052% 224% --
LLCS: [Chrerrplzon] [Choerephon]
Rate LCS:LLCS AD:LCS_length AD:XS:LCS_length LCS:BV:LLCS
LCS:LLCS 11270/s -- -70% -70% -92%
AD:LCS_length 37594/s 234% -- -1% -75%
AD:XS:LCS_length 38059/s 238% 1% -- -74%
LCS:BV:LLCS 148945/s 1222% 296% 291% --
LLCS: [qw/a b d/ x 50], [qw/b a d c/ x 50]
Rate LCS:LLCS AD:LCS_length AD:XS:LCS_length LCS:BV:LLCS
LCS:LLCS 50.0/s -- -37% -37% -98%
AD:LCS_length 79.2/s 58% -- -1% -97%
AD:XS:LCS_length 79.8/s 60% 1% -- -97%
LCS:BV:LLCS 2357/s 4614% 2874% 2853% --
SOURCE REPOSITORY
http://github.com/wollmers/LCS-BV
SEE ALSO
Algorithm::Diff LCS LCS::Tiny
AUTHOR
Helmut Wollmersdorfer
COPYRIGHT AND LICENSE
Copyright 2014-2020 by Helmut Wollmersdorfer
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.