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unit randomunit;
{$mode objfpc}{$H+}
interface
uses
Classes, SysUtils;
type
tMersenneTwister = class
private
state: array[0..623] of longword;
index: longint;
public
procedure init(seed: longword);
function extract_number: longword;
function random(ma: longword): longword; overload;
function random: extended; overload;
procedure generate_numbers;
end;
implementation
// tMersenneTwister ************************************************************
procedure tMersenneTwister.init(seed: longword);
var
i: longint;
begin
index:=0;
state[0]:=seed;
for i:=1 to 623 do
state[i]:=longword($ffffffff and (qword(1812433253) * qword(state[i-1] xor state[i-1] shr 30) + i)); // 0x6c078965
end;
function tMersenneTwister.extract_number: longword;
begin
if index=0 then
generate_numbers;
result:=state[index];
result:=result xor (result shr 11);
result:=result xor longword(qword(result shl 7) and 2636928640); // 0x9d2c5680
result:=result xor longword(qword(result shl 15) and 4022730752); // 0xefc60000
result:=result xor (result shr 18);
index := (index + 1) mod 624;
end;
function tMersenneTwister.random(ma: longword): longword;
var
i: longword;
begin
repeat
i:=extract_number;
until i<((high(longword)+1) div qword(ma))*ma;
result:=i mod ma;
end;
function tMersenneTwister.random: extended;
begin
result:=(extract_number/(high(longword)+1) + extract_number)/(high(longword)+1);
end;
procedure tMersenneTwister.generate_numbers;
var
i,y: longint;
begin
for i:=0 to 623 do begin
y:=longint((state[i] and $80000000) or // bit 31 (32nd bit) of MT[i]
(state[(i+1) mod 624] and $7fffffff)); // bits 0-30 (first 31 bits) of MT[...]
state[i]:=state[(i + 397) mod 624] xor (y shr 1);
if odd(y) then
state[i]:=longword(state[i] xor 2567483615); // 0x9908b0df
end;
end;
end.
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