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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- G N A T . M B B S _ F L O A T _ R A N D O M --
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6 -- --
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7 -- S p e c --
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8 -- --
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145
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9 -- Copyright (C) 1992-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- This specification is derived from the Ada Reference Manual for use with --
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12 -- GNAT. The copyright notice above, and the license provisions that follow --
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13 -- apply solely to the contents of the part following the private keyword. --
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14 -- --
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15 -- GNAT is free software; you can redistribute it and/or modify it under --
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16 -- terms of the GNU General Public License as published by the Free Soft- --
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17 -- ware Foundation; either version 3, or (at your option) any later ver- --
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18 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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19 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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20 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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21 -- --
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22 -- As a special exception under Section 7 of GPL version 3, you are granted --
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23 -- additional permissions described in the GCC Runtime Library Exception, --
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24 -- version 3.1, as published by the Free Software Foundation. --
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25 -- --
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26 -- You should have received a copy of the GNU General Public License and --
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27 -- a copy of the GCC Runtime Library Exception along with this program; --
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28 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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29 -- <http://www.gnu.org/licenses/>. --
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30 -- --
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31 -- GNAT was originally developed by the GNAT team at New York University. --
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32 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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33 -- --
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34 ------------------------------------------------------------------------------
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35
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36 -- The implementation used in this package was contributed by
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37 -- Robert Eachus. It is based on the work of L. Blum, M. Blum, and
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38 -- M. Shub, SIAM Journal of Computing, Vol 15. No 2, May 1986. The
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39 -- particular choices for P and Q chosen here guarantee a period of
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40 -- 562,085,314,430,582 (about 2**49), and the generated sequence has
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41 -- excellent randomness properties. For further details, see the
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42 -- paper "Fast Generation of Trustworthy Random Numbers", by Robert
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43 -- Eachus, which describes both the algorithm and the efficient
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44 -- implementation approach used here.
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45
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46 -- Formerly, this package was Ada.Numerics.Float_Random. It is retained
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47 -- here in part to allow users to reconstruct number sequences generated
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48 -- by previous versions.
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49
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50 with Interfaces;
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51
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52 package GNAT.MBBS_Float_Random is
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53
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54 -- Basic facilities
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55
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56 type Generator is limited private;
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57
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58 subtype Uniformly_Distributed is Float range 0.0 .. 1.0;
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59
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60 function Random (Gen : Generator) return Uniformly_Distributed;
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61
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62 procedure Reset (Gen : Generator);
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63 procedure Reset (Gen : Generator; Initiator : Integer);
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64
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65 -- Advanced facilities
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66
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67 type State is private;
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68
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69 procedure Save (Gen : Generator; To_State : out State);
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70 procedure Reset (Gen : Generator; From_State : State);
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71
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72 Max_Image_Width : constant := 80;
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73
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74 function Image (Of_State : State) return String;
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75 function Value (Coded_State : String) return State;
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76
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77 private
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78 type Int is new Interfaces.Integer_32;
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79
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80 -- We prefer to use 14 digits for Flt, but some targets are more limited
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81
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82 type Flt is digits Positive'Min (14, Long_Long_Float'Digits);
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83
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84 K1 : constant := 94_833_359;
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85 K1F : constant := 94_833_359.0;
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86 K2 : constant := 47_416_679;
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87 K2F : constant := 47_416_679.0;
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88 Scal : constant := 1.0 / (K1F * K2F);
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89
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90 type State is record
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91 X1 : Int := 2999 ** 2; -- Square mod p
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92 X2 : Int := 1439 ** 2; -- Square mod q
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93 P : Int := K1;
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94 Q : Int := K2;
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95 X : Int := 1;
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96 Scl : Flt := Scal;
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97 end record;
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98
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99 type Generator is limited record
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100 Gen_State : State;
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101 end record;
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102
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103 end GNAT.MBBS_Float_Random;
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