File : g-mbflra.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT RUN-TIME COMPONENTS --
4 -- --
5 -- G N A T . M B B S _ F L O A T _ R A N D O M --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
10 -- --
11 -- This specification is derived from the Ada Reference Manual for use with --
12 -- GNAT. The copyright notice above, and the license provisions that follow --
13 -- apply solely to the contents of the part following the private keyword. --
14 -- --
15 -- GNAT is free software; you can redistribute it and/or modify it under --
16 -- terms of the GNU General Public License as published by the Free Soft- --
17 -- ware Foundation; either version 3, or (at your option) any later ver- --
18 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
19 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
20 -- or FITNESS FOR A PARTICULAR PURPOSE. --
21 -- --
22 -- --
23 -- --
24 -- --
25 -- --
26 -- You should have received a copy of the GNU General Public License and --
27 -- a copy of the GCC Runtime Library Exception along with this program; --
28 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
29 -- <http://www.gnu.org/licenses/>. --
30 -- --
31 -- GNAT was originally developed by the GNAT team at New York University. --
32 -- Extensive contributions were provided by Ada Core Technologies Inc. --
33 -- --
34 ------------------------------------------------------------------------------
35
36 -- The implementation used in this package was contributed by
37 -- Robert Eachus. It is based on the work of L. Blum, M. Blum, and
38 -- M. Shub, SIAM Journal of Computing, Vol 15. No 2, May 1986. The
39 -- particular choices for P and Q chosen here guarantee a period of
40 -- 562,085,314,430,582 (about 2**49), and the generated sequence has
41 -- excellent randomness properties. For further details, see the
42 -- paper "Fast Generation of Trustworthy Random Numbers", by Robert
43 -- Eachus, which describes both the algorithm and the efficient
44 -- implementation approach used here.
45
46 -- Formerly, this package was Ada.Numerics.Float_Random. It is retained
47 -- here in part to allow users to reconstruct number sequences generated
48 -- by previous versions.
49
50 with Interfaces;
51
52 package GNAT.MBBS_Float_Random is
53
54 -- Basic facilities
55
56 type Generator is limited private;
57
58 subtype Uniformly_Distributed is Float range 0.0 .. 1.0;
59
60 function Random (Gen : Generator) return Uniformly_Distributed;
61
62 procedure Reset (Gen : Generator);
63 procedure Reset (Gen : Generator; Initiator : Integer);
64
65 -- Advanced facilities
66
67 type State is private;
68
69 procedure Save (Gen : Generator; To_State : out State);
70 procedure Reset (Gen : Generator; From_State : State);
71
72 Max_Image_Width : constant := 80;
73
74 function Image (Of_State : State) return String;
75 function Value (Coded_State : String) return State;
76
77 private
78 type Int is new Interfaces.Integer_32;
79
80 -- We prefer to use 14 digits for Flt, but some targets are more limited
81
82 type Flt is digits Positive'Min (14, Long_Long_Float'Digits);
83
84 K1 : constant := 94_833_359;
85 K1F : constant := 94_833_359.0;
86 K2 : constant := 47_416_679;
87 K2F : constant := 47_416_679.0;
88 Scal : constant := 1.0 / (K1F * K2F);
89
90 type State is record
91 X1 : Int := 2999 ** 2; -- Square mod p
92 X2 : Int := 1439 ** 2; -- Square mod q
93 P : Int := K1;
94 Q : Int := K2;
95 X : Int := 1;
96 Scl : Flt := Scal;
97 end record;
98
99 type Generator is limited record
100 Gen_State : State;
101 end record;
102
103 end GNAT.MBBS_Float_Random;