104 lines
4.7 KiB
Ada
104 lines
4.7 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME COMPONENTS --
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-- --
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-- G N A T . M B B S _ F L O A T _ R A N D O M --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
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-- --
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-- This specification is derived from the Ada Reference Manual for use with --
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-- GNAT. The copyright notice above, and the license provisions that follow --
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-- apply solely to the contents of the part following the private keyword. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- The implementation used in this package was contributed by
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-- Robert Eachus. It is based on the work of L. Blum, M. Blum, and
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-- M. Shub, SIAM Journal of Computing, Vol 15. No 2, May 1986. The
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-- particular choices for P and Q chosen here guarantee a period of
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-- 562,085,314,430,582 (about 2**49), and the generated sequence has
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-- excellent randomness properties. For further details, see the
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-- paper "Fast Generation of Trustworthy Random Numbers", by Robert
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-- Eachus, which describes both the algorithm and the efficient
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-- implementation approach used here.
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-- Formerly, this package was Ada.Numerics.Float_Random. It is retained
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-- here in part to allow users to reconstruct number sequences generated
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-- by previous versions.
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with Interfaces;
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package GNAT.MBBS_Float_Random is
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-- Basic facilities
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type Generator is limited private;
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subtype Uniformly_Distributed is Float range 0.0 .. 1.0;
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function Random (Gen : Generator) return Uniformly_Distributed;
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procedure Reset (Gen : Generator);
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procedure Reset (Gen : Generator; Initiator : Integer);
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-- Advanced facilities
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type State is private;
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procedure Save (Gen : Generator; To_State : out State);
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procedure Reset (Gen : Generator; From_State : State);
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Max_Image_Width : constant := 80;
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function Image (Of_State : State) return String;
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function Value (Coded_State : String) return State;
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private
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type Int is new Interfaces.Integer_32;
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-- We prefer to use 14 digits for Flt, but some targets are more limited
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type Flt is digits Positive'Min (14, Long_Long_Float'Digits);
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K1 : constant := 94_833_359;
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K1F : constant := 94_833_359.0;
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K2 : constant := 47_416_679;
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K2F : constant := 47_416_679.0;
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Scal : constant := 1.0 / (K1F * K2F);
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type State is record
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X1 : Int := 2999 ** 2; -- Square mod p
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X2 : Int := 1439 ** 2; -- Square mod q
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P : Int := K1;
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Q : Int := K2;
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X : Int := 1;
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Scl : Flt := Scal;
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end record;
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type Generator is limited record
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Gen_State : State;
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end record;
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end GNAT.MBBS_Float_Random;
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