1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
#############################################################################
##
#W random.g GAP library Martin Schoenert
##
#H @(#)$Id: random.g,v 4.3.2.1 2004/01/12 16:58:00 gap Exp $
##
#Y Copyright (C) 1996, Lehrstuhl D fuer Mathematik, RWTH Aachen, Germany
#Y (C) 1998 School Math and Comp. Sci., University of St. Andrews, Scotland
#Y Copyright (C) 2002 The GAP Group
##
## This file contains the random number generator
##
Revision.random_g :=
"@(#)$Id: random.g,v 4.3.2.1 2004/01/12 16:58:00 gap Exp $";
#############################################################################
##
#F RANDOM_LIST( <list> ) . . . . . . . . return a random element from a list
##
R_N := 1;
R_X := [];
# 268435456 is 2^28. This way
# we avoid recomputing it every time we need it.
R_228 := 2^28;
RANDOM_LIST := function ( list )
R_N := R_N mod 55 + 1;
R_X[R_N] := (R_X[R_N] + R_X[(R_N+30) mod 55+1]) mod R_228;
return list[ QUO_INT( R_X[R_N] * LEN_LIST(list), R_228 ) + 1 ];
end;
RANDOM_SEED := function ( n )
local i;
R_N := 1; R_X := [ n mod R_228 ];
for i in [2..55] do
R_X[i] := (1664525 * R_X[i-1] + 1) mod R_228;
od;
for i in [1..99] do
R_N := R_N mod 55 + 1;
R_X[R_N] := (R_X[R_N] + R_X[(R_N+30) mod 55+1]) mod R_228;
od;
end;
if R_X = [] then RANDOM_SEED( 1 ); fi;
#############################################################################
##
#E random.g . . . . . . . . . . . . . . . . . . . . . . . . . . . ends here
##
|
