gcc/ada/a-nuflra.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --            A D A . N U M E R I C S . F L O A T _ R A N D O M             --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2009, 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 -- As a special exception under Section 7 of GPL version 3, you are granted --
  23 -- additional permissions described in the GCC Runtime Library Exception,   --
  24 -- version 3.1, as published by the Free Software Foundation.               --
  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 --  Note: 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 with Interfaces;
  47
  48 package Ada.Numerics.Float_Random is
  49
  50    --  Basic facilities
  51
  52    type Generator is limited private;
  53
  54    subtype Uniformly_Distributed is Float range 0.0 .. 1.0;
  55
  56    function Random (Gen : Generator) return Uniformly_Distributed;
  57
  58    procedure Reset (Gen : Generator);
  59    procedure Reset (Gen : Generator; Initiator : Integer);
  60
  61    --  Advanced facilities
  62
  63    type State is private;
  64
  65    procedure Save  (Gen : Generator; To_State   : out State);
  66    procedure Reset (Gen : Generator; From_State : State);
  67
  68    Max_Image_Width : constant := 80;
  69
  70    function Image (Of_State    : State)  return String;
  71    function Value (Coded_State : String) return State;
  72
  73 private
  74    type Int is new Interfaces.Integer_32;
  75
  76    --  We prefer to use 14 digits for Flt, but some targets are more limited
  77
  78    type Flt is digits Positive'Min (14, Long_Long_Float'Digits);
  79
  80    K1   : constant := 94_833_359;
  81    K1F  : constant := 94_833_359.0;
  82    K2   : constant := 47_416_679;
  83    K2F  : constant := 47_416_679.0;
  84    Scal : constant := 1.0 / (K1F * K2F);
  85
  86    type State is record
  87       X1  : Int := 2999 ** 2;      --  Square mod p
  88       X2  : Int := 1439 ** 2;      --  Square mod q
  89       P   : Int := K1;
  90       Q   : Int := K2;
  91       X   : Int := 1;
  92       Scl : Flt := Scal;
  93    end record;
  94
  95    type Generator is limited record
  96       Gen_State : State;
  97    end record;
  98
  99 end Ada.Numerics.Float_Random;