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------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- A D A . N U M E R I C S . D I S C R E T E _ R A N D O M -- -- -- -- S p e c -- -- -- -- Copyright (C) 1992-2009, Free Software Foundation, Inc. -- -- -- -- This specification is derived from the Ada Reference Manual for use with -- -- GNAT. The copyright notice above, and the license provisions that follow -- -- apply solely to the contents of the part following the private keyword. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- <http://www.gnu.org/licenses/>. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- Note: the implementation used in this package was contributed by Robert -- Eachus. It is based on the work of L. Blum, M. Blum, and M. Shub, SIAM -- Journal of Computing, Vol 15. No 2, May 1986. The particular choices for P -- and Q chosen here guarantee a period of 562,085,314,430,582 (about 2**49), -- and the generated sequence has excellent randomness properties. For further -- details, see the paper "Fast Generation of Trustworthy Random Numbers", by -- Robert Eachus, which describes both the algorithm and the efficient -- implementation approach used here. with Interfaces; generic type Result_Subtype is (<>); package Ada.Numerics.Discrete_Random is -- The algorithm used here is reliable from a required statistical point of -- view only up to 48 bits. We try to behave reasonably in the case of -- larger types, but we can't guarantee the required properties. So -- generate a warning for these (slightly) dubious cases. pragma Compile_Time_Warning (Result_Subtype'Size > 48, "statistical properties not guaranteed for size > 48"); -- Basic facilities type Generator is limited private; function Random (Gen : Generator) return Result_Subtype; procedure Reset (Gen : Generator); procedure Reset (Gen : Generator; Initiator : Integer); -- Advanced facilities type State is private; procedure Save (Gen : Generator; To_State : out State); procedure Reset (Gen : Generator; From_State : State); Max_Image_Width : constant := 80; function Image (Of_State : State) return String; function Value (Coded_State : String) return State; private subtype Int is Interfaces.Integer_32; subtype Rst is Result_Subtype; -- We prefer to use 14 digits for Flt, but some targets are more limited type Flt is digits Positive'Min (14, Long_Long_Float'Digits); RstF : constant Flt := Flt (Rst'Pos (Rst'First)); RstL : constant Flt := Flt (Rst'Pos (Rst'Last)); Offs : constant Flt := RstF - 0.5; K1 : constant := 94_833_359; K1F : constant := 94_833_359.0; K2 : constant := 47_416_679; K2F : constant := 47_416_679.0; Scal : constant Flt := (RstL - RstF + 1.0) / (K1F * K2F); type State is record X1 : Int := Int (2999 ** 2); X2 : Int := Int (1439 ** 2); P : Int := K1; Q : Int := K2; FP : Flt := K1F; Scl : Flt := Scal; end record; type Generator is limited record Gen_State : State; end record; end Ada.Numerics.Discrete_Random;