1 files changed, 80 insertions, 0 deletions
diff --git a/randomunit.pas b/randomunit.pas
new file mode 100644
index 0000000..2b665f0
--- /dev/null
+++ b/randomunit.pas
@@ -0,0 +1,80 @@
+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.
+