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) 1992-2002 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 2,  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.  See the GNU General Public License --
  21 -- for  more details.  You should have  received  a copy of the GNU General --
  22 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  23 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  24 -- MA 02111-1307, USA.                                                      --
  25 --                                                                          --
  26 -- As a special exception,  if other files  instantiate  generics from this --
  27 -- unit, or you link  this unit with other files  to produce an executable, --
  28 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  29 -- covered  by the  GNU  General  Public  License.  This exception does not --
  30 -- however invalidate  any other reasons why  the executable file  might be --
  31 -- covered by the  GNU Public License.                                      --
  32 --                                                                          --
  33 -- GNAT was originally developed  by the GNAT team at  New York University. --
  34 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  35 --                                                                          --
  36 ------------------------------------------------------------------------------
  37
  38 --  Note: the implementation used in this package was contributed by
  39 --  Robert Eachus. It is based on the work of L. Blum, M. Blum, and
  40 --  M. Shub, SIAM Journal of Computing, Vol 15. No 2, May 1986. The
  41 --  particular choices for P and Q chosen here guarantee a period of
  42 --  562,085,314,430,582 (about 2**49), and the generated sequence has
  43 --  excellent randomness properties. For further details, see the
  44 --  paper "Fast Generation of Trustworthy Random Numbers", by Robert
  45 --  Eachus, which describes both the algorithm and the efficient
  46 --  implementation approach used here.
  47
  48 with Interfaces;
  49
  50 package Ada.Numerics.Float_Random is
  51
  52    --  Basic facilities
  53
  54    type Generator is limited private;
  55
  56    subtype Uniformly_Distributed is Float range 0.0 .. 1.0;
  57
  58    function Random (Gen : Generator) return Uniformly_Distributed;
  59
  60    procedure Reset (Gen : Generator);
  61    procedure Reset (Gen : Generator; Initiator : Integer);
  62
  63    --  Advanced facilities
  64
  65    type State is private;
  66
  67    procedure Save  (Gen : Generator; To_State   : out State);
  68    procedure Reset (Gen : Generator; From_State : State);
  69
  70    Max_Image_Width : constant := 80;
  71
  72    function Image (Of_State :    State)  return String;
  73    function Value (Coded_State : String) return State;
  74
  75 private
  76    type Int is new Interfaces.Integer_32;
  77
  78    --  We prefer to use 14 digits for Flt, but some targets are more limited
  79
  80    type Flt is digits Positive'Min (14, Long_Long_Float'Digits);
  81
  82    K1   : constant := 94_833_359;
  83    K1F  : constant := 94_833_359.0;
  84    K2   : constant := 47_416_679;
  85    K2F  : constant := 47_416_679.0;
  86    Scal : constant := 1.0 / (K1F * K2F);
  87
  88    type State is record
  89       X1  : Int := 2999 ** 2;      --  Square mod p
  90       X2  : Int := 1439 ** 2;      --  Square mod q
  91       P   : Int := K1;
  92       Q   : Int := K2;
  93       X   : Int := 1;
  94       Scl : Flt := Scal;
  95    end record;
  96
  97    type Generator is limited record
  98       Gen_State : State;
  99    end record;
 100
 101 end Ada.Numerics.Float_Random;