a hash function for board games
Perl 6
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README.md

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NAME

Algorithm::ZobristHashing - a hash function for board games

SYNOPSIS

use Algorithm::ZobristHashing;

# the case input is Str
my $zobrist = Algorithm::ZobristHashing.new();
my $status = $zobrist.encode("Perl6 is fun");
my $code = $zobrist.get(0,"P"); # Int value which represents state h(0,"P")
my $code = $zobrist.get(5," "); # Int value which represents state h(5," ")

# the case input is Array
my $zobrist = Algorithm::ZobristHashing.new();
my $status = $zobrist.encode([["Perl6"],["is"],["fun"]]);
my $code = $zobrist.get(0,"Perl6"); # Int value which represents state h(0,"Perl6")

DESCRIPTION

Algorithm::ZobristHashing is a hash function for board games such as chess, GO, GO-MOKU, tic-tac-toe, and so on.

CONSTRUCTOR

new

my $zobrist = Algorithm::ZobristHashing.new(%options);

OPTIONS

  • max-rand => $max-rand

Sets the upper bound number for generating random number. Default is 1e9.

METHODS

encode(Str|Array)

my $status = $zobrist.encode("abc"); # h(0,"a") xor h(1,"b") xor h(2,"c")
my $status = $zobrist.encode([["a"],["b"],["c"]]); # h(0,"a") xor h(1,"b") xor h(2,"c")
my $status = $zobrist.encode([["ab"],["c"]]); # h(0,"ab") xor h(1,"c")

Returns the hash value which represents the status of the input sequence. If the input value is the nested array, it flattens this and handles as a 1-dimensional array. If the input value is empty, it returns the type object Int.

get(Int $position, Str $type)

my $status = $zobrist.encode(["abc"]);
my $code = $zobrist.get(0,"abc"); # in this case $code == $status
my $new-code = $zobrist.get(0,"perl"); # assigns a new rand value, since h(0,"perl") is not yet encoded

Returns the Int value which represents the state(i.e position-type pair). If it intends to get the state not yet encoded, it assigns a new rand value to the state and returns this new value.

AUTHOR

titsuki titsuki@cpan.org

COPYRIGHT AND LICENSE

Copyright 2016 titsuki

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.

This algorithm is from Zobrist, Albert L. "A new hashing method with application for game playing." ICCA journal 13.2 (1970): 69-73.