1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- G N A T . R A N D O M _ N U M B E R S --
9 -- Copyright (C) 2007, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 with Ada.Numerics.Long_Elementary_Functions;
35 use Ada.Numerics.Long_Elementary_Functions;
36 with Ada.Unchecked_Conversion;
37 with System.Random_Numbers; use System.Random_Numbers;
39 package body GNAT.Random_Numbers is
41 Sys_Max_Image_Width : constant := System.Random_Numbers.Max_Image_Width;
43 subtype Image_String is String (1 .. Max_Image_Width);
45 -- Utility function declarations
47 procedure Insert_Image
48 (S : in out Image_String;
51 -- Insert string representation of V in S starting at position Index
58 new Ada.Unchecked_Conversion (Unsigned_32, Integer_32);
60 new Ada.Unchecked_Conversion (Unsigned_64, Integer_64);
66 procedure Insert_Image
67 (S : in out Image_String;
71 Image : constant String := Integer_64'Image (V);
73 S (Index .. Index + Image'Length - 1) := Image;
80 function Random_Discrete
82 Min : Result_Subtype := Default_Min;
83 Max : Result_Subtype := Result_Subtype'Last) return Result_Subtype
86 new System.Random_Numbers.Random_Discrete
87 (Result_Subtype, Default_Min);
89 return F (Gen.Rep, Min, Max);
96 function Random (Gen : Generator) return Float is
98 return Random (Gen.Rep);
101 function Random (Gen : Generator) return Long_Float is
103 return Random (Gen.Rep);
106 function Random (Gen : Generator) return Interfaces.Unsigned_32 is
108 return Random (Gen.Rep);
111 function Random (Gen : Generator) return Interfaces.Unsigned_64 is
113 return Random (Gen.Rep);
116 function Random (Gen : Generator) return Integer_64 is
118 return To_Signed (Unsigned_64'(Random (Gen)));
121 function Random (Gen : Generator) return Integer_32 is
123 return To_Signed (Unsigned_32'(Random (Gen)));
126 function Random (Gen : Generator) return Long_Integer is
127 function Random_Long_Integer is new Random_Discrete (Long_Integer);
129 return Random_Long_Integer (Gen);
132 function Random (Gen : Generator) return Integer is
133 function Random_Integer is new Random_Discrete (Integer);
135 return Random_Integer (Gen);
142 function Random_Float (Gen : Generator) return Result_Subtype is
143 function F is new System.Random_Numbers.Random_Float (Result_Subtype);
148 ---------------------
149 -- Random_Gaussian --
150 ---------------------
152 -- Generates pairs of normally distributed values using the polar method of
153 -- G. E. P. Box, M. E. Muller, and G. Marsaglia. See Donald E. Knuth, The
154 -- Art of Computer Programming, Vol 2: Seminumerical Algorithms, section
155 -- 3.4.1, subsection C, algorithm P. Returns half of the pair on each call,
156 -- using the Next_Gaussian field of Gen to hold the second member on
157 -- even-numbered calls.
159 function Random_Gaussian (Gen : Generator) return Long_Float is
160 G : Generator renames Gen'Unrestricted_Access.all;
162 V1, V2, Rad2, Mult : Long_Float;
165 if G.Have_Gaussian then
166 G.Have_Gaussian := False;
167 return G.Next_Gaussian;
171 V1 := 2.0 * Random (G) - 1.0;
172 V2 := 2.0 * Random (G) - 1.0;
173 Rad2 := V1 ** 2 + V2 ** 2;
174 exit when Rad2 < 1.0 and then Rad2 /= 0.0;
177 -- Now V1 and V2 are coordinates in the unit circle
179 Mult := Sqrt (-2.0 * Log (Rad2) / Rad2);
180 G.Next_Gaussian := V2 * Mult;
181 G.Have_Gaussian := True;
182 return Long_Float'Machine (V1 * Mult);
186 function Random_Gaussian (Gen : Generator) return Float is
187 V : constant Long_Float := Random_Gaussian (Gen);
189 return Float'Machine (Float (V));
196 procedure Reset (Gen : out Generator) is
199 Gen.Have_Gaussian := False;
203 (Gen : out Generator;
204 Initiator : Initialization_Vector)
207 Reset (Gen.Rep, Initiator);
208 Gen.Have_Gaussian := False;
212 (Gen : out Generator;
213 Initiator : Interfaces.Integer_32)
216 Reset (Gen.Rep, Initiator);
217 Gen.Have_Gaussian := False;
221 (Gen : out Generator;
222 Initiator : Interfaces.Unsigned_32)
225 Reset (Gen.Rep, Initiator);
226 Gen.Have_Gaussian := False;
230 (Gen : out Generator;
234 Reset (Gen.Rep, Initiator);
235 Gen.Have_Gaussian := False;
239 (Gen : out Generator;
240 From_State : Generator)
243 Reset (Gen.Rep, From_State.Rep);
244 Gen.Have_Gaussian := From_State.Have_Gaussian;
245 Gen.Next_Gaussian := From_State.Next_Gaussian;
248 Frac_Scale : constant Long_Float :=
250 (Long_Float'Machine_Radix) ** Long_Float'Machine_Mantissa;
252 function Val64 (Image : String) return Integer_64;
253 -- Renames Integer64'Value
254 -- We cannot use a 'renames Integer64'Value' since for some strange
255 -- reason, this requires a dependency on s-auxdec.ads which not all
256 -- run-times support ???
258 function Val64 (Image : String) return Integer_64 is
260 return Integer_64'Value (Image);
264 (Gen : out Generator;
267 F0 : constant Integer := From_Image'First;
268 T0 : constant Integer := From_Image'First + Sys_Max_Image_Width;
271 Reset (Gen.Rep, From_Image (F0 .. F0 + Sys_Max_Image_Width));
273 if From_Image (T0 + 1) = '1' then
274 Gen.Have_Gaussian := True;
276 Long_Float (Val64 (From_Image (T0 + 3 .. T0 + 23))) / Frac_Scale
277 * Long_Float (Long_Float'Machine_Radix)
278 ** Integer (Val64 (From_Image (T0 + 25 .. From_Image'Last)));
280 Gen.Have_Gaussian := False;
288 function Image (Gen : Generator) return String is
289 Result : Image_String;
292 Result := (others => ' ');
293 Result (1 .. Sys_Max_Image_Width) := Image (Gen.Rep);
295 if Gen.Have_Gaussian then
296 Result (Sys_Max_Image_Width + 2) := '1';
297 Insert_Image (Result, Sys_Max_Image_Width + 4,
298 Integer_64 (Long_Float'Fraction (Gen.Next_Gaussian)
300 Insert_Image (Result, Sys_Max_Image_Width + 24,
301 Integer_64 (Long_Float'Exponent (Gen.Next_Gaussian)));
304 Result (Sys_Max_Image_Width + 2) := '0';
310 end GNAT.Random_Numbers;