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 -- Extended pseudo-random number generation
36 -- This package provides a type representing pseudo-random number generators,
37 -- and subprograms to extract various distributions of numbers from them. It
38 -- also provides types for representing initialization values and snapshots of
39 -- internal generator state, which permit reproducible pseudo-random streams.
41 -- The generator currently provided by this package has an extremely long
42 -- period (at least 2**19937-1), and passes the Big Crush test suite, with the
43 -- exception of the two linear complexity tests. Therefore, it is suitable for
44 -- simulations, but should not be used as a cryptographic pseudo-random source
45 -- without additional processing.
47 -- The design of this package effects is simplified compared to the design
48 -- of standard Ada.Numerics packages. There is no separate State type; the
49 -- Generator type itself suffices for this purpose. The parameter modes on
50 -- Reset procedures better reflect the effect of these routines.
52 with System
.Random_Numbers
;
53 with Interfaces
; use Interfaces
;
55 package GNAT
.Random_Numbers
is
57 type Generator
is limited private;
58 subtype Initialization_Vector
is
59 System
.Random_Numbers
.Initialization_Vector
;
61 function Random
(Gen
: Generator
) return Float;
62 function Random
(Gen
: Generator
) return Long_Float;
63 -- Return pseudo-random numbers uniformly distributed on [0 .. 1)
65 function Random
(Gen
: Generator
) return Interfaces
.Integer_32
;
66 function Random
(Gen
: Generator
) return Interfaces
.Unsigned_32
;
67 function Random
(Gen
: Generator
) return Interfaces
.Integer_64
;
68 function Random
(Gen
: Generator
) return Interfaces
.Unsigned_64
;
69 function Random
(Gen
: Generator
) return Integer;
70 function Random
(Gen
: Generator
) return Long_Integer;
71 -- Return pseudo-random numbers uniformly distributed on T'First .. T'Last
72 -- for various builtin integer types.
75 type Result_Subtype
is (<>);
76 Default_Min
: Result_Subtype
:= Result_Subtype
'Val (0);
77 function Random_Discrete
79 Min
: Result_Subtype
:= Default_Min
;
80 Max
: Result_Subtype
:= Result_Subtype
'Last) return Result_Subtype
;
81 -- Returns pseudo-random numbers uniformly distributed on Min .. Max
84 type Result_Subtype
is digits <>;
85 function Random_Float
(Gen
: Generator
) return Result_Subtype
;
86 -- Returns pseudo-random numbers uniformly distributed on [0 .. 1)
88 function Random_Gaussian
(Gen
: Generator
) return Long_Float;
89 function Random_Gaussian
(Gen
: Generator
) return Float;
90 -- Returns pseudo-random numbers normally distributed value with mean 0
91 -- and standard deviation 1.0.
93 procedure Reset
(Gen
: out Generator
);
94 -- Re-initialize the state of Gen from the time of day
98 Initiator
: Initialization_Vector
);
100 (Gen
: out Generator
;
101 Initiator
: Interfaces
.Integer_32
);
103 (Gen
: out Generator
;
104 Initiator
: Interfaces
.Unsigned_32
);
106 (Gen
: out Generator
;
107 Initiator
: Integer);
108 -- Re-initialize Gen based on the Initiator in various ways. Identical
109 -- values of Initiator cause identical sequences of values.
111 procedure Reset
(Gen
: out Generator
; From_State
: Generator
);
112 -- Causes the state of Gen to be identical to that of From_State; Gen
113 -- and From_State will produce identical sequences of values subsequently.
115 procedure Reset
(Gen
: out Generator
; From_Image
: String);
116 function Image
(Gen
: Generator
) return String;
118 -- Reset (Gen2, Image (Gen1))
119 -- has the same effect as Reset (Gen2, Gen1);
121 Max_Image_Width
: constant :=
122 System
.Random_Numbers
.Max_Image_Width
+ 2 + 20 + 5;
123 -- Maximum possible length of result of Image (...)
127 type Generator
is limited record
128 Rep
: System
.Random_Numbers
.Generator
;
130 Have_Gaussian
: Boolean;
131 -- The algorithm used for Random_Gaussian produces deviates in
132 -- pairs. Have_Gaussian is true iff Random_Gaussian has returned one
133 -- member of the pair and Next_Gaussian contains the other.
135 Next_Gaussian
: Long_Float;
136 -- Next random deviate to be produced by Random_Gaussian, if
140 end GNAT
.Random_Numbers
;