MersenneTwister

MT.pl

use strict;

# MT19937
my $w = 32;
my $n = 624;
my $m = 397;
my $r = 31;
my $u = 11;
my $s = 7;
my $t = 15;
my $l = 18;
my $a = 0x9908B0DF;
my $b = 0x9D2C5680;
my $c = 0xEFC60000;

# MT内部状態
my $i = 0;
my @x = ();

# ビットマスクの準備
my $mask_u = 0;
my $mask_l = 0;
for(my $j = 0; $j < $w; $j++){
	$mask_u = ($mask_u << 1) + ($j < $w - $r);
	$mask_l = ($mask_l << 1) + ($j >= $w - $r);
}

# seedを受け取ってxを初期化 (mt19937ar.cに準拠)
sub init_genrand {
	my($seed) = @_;
	$x[0] = $seed & 0xFFFFFFFF;
	for(my $j = 1; $j < $n; $j++){
		$x[$j] = (1812433253 * ($x[$j-1] ^ ($x[$j-1] >> 30)) + $j) & 0xFFFFFFFF; 
	}
}

# 乱数を生成
sub genrand_int {
	# Step.1
	my $z = ($x[$i] & $mask_u | $x[($i+1) % $n] & $mask_l);
	
	# Step.2
	$x[$i] = $x[($i+$m) % $n] ^ ($z >> 1) ^ (($z & 1) == 0 ? 0 : $a);
	
	# Step.3
	my $y = $x[$i];
	$y = $y ^ ($y >> $u);
	$y = $y ^ (($y << $s) & $b);
	$y = $y ^ (($y << $t) & $c);
	$y = $y ^ ($y >> $l);
	
	# カウンタを変更して、生成した乱数を返す
	$i = ($i+1) % $n;
	return $y;
}

# 使ってみる
init_genrand(20150919);
for(my $j = 1; $j <= 1024; $j++){
	print $j, ": ", genrand_int(), "\n";
}