diff options
Diffstat (limited to 'gcc/ada/a-nudira.adb')
-rw-r--r-- | gcc/ada/a-nudira.adb | 260 |
1 files changed, 32 insertions, 228 deletions
diff --git a/gcc/ada/a-nudira.adb b/gcc/ada/a-nudira.adb index 87abcd8f100..e17945c07a2 100644 --- a/gcc/ada/a-nudira.adb +++ b/gcc/ada/a-nudira.adb @@ -6,7 +6,7 @@ -- -- -- B o d y -- -- -- --- Copyright (C) 1992-2009, Free Software Foundation, Inc. -- +-- Copyright (C) 1992-2010, Free Software Foundation, Inc. -- -- -- -- 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- -- @@ -29,9 +29,7 @@ -- -- ------------------------------------------------------------------------------ -with Ada.Calendar; - -with Interfaces; use Interfaces; +with System.Random_Numbers; use System.Random_Numbers; package body Ada.Numerics.Discrete_Random is @@ -49,249 +47,55 @@ package body Ada.Numerics.Discrete_Random is -- get a pointer to the state in the passed Generator. This works because -- Generator is a limited type and will thus always be passed by reference. - type Pointer is access all State; - - Fits_In_32_Bits : constant Boolean := - Rst'Size < 31 - or else (Rst'Size = 31 - and then Rst'Pos (Rst'First) < 0); - -- This is set True if we do not need more than 32 bits in the result. If - -- we need 64-bits, we will only use the meaningful 48 bits of any 64-bit - -- number generated, since if more than 48 bits are required, we split the - -- computation into two separate parts, since the algorithm does not behave - -- above 48 bits. - - -- The way this expression works is that obviously if the size is 31 bits, - -- it fits in 32 bits. In the 32-bit case, it fits in 32-bit signed if the - -- range has negative values. It is too conservative in the case that the - -- programmer has set a size greater than the default, e.g. a size of 33 - -- for an integer type with a range of 1..10, but an over-conservative - -- result is OK. The important thing is that the value is only True if - -- we know the result will fit in 32-bits signed. If the value is False - -- when it could be True, the behavior will be correct, just a bit less - -- efficient than it could have been in some unusual cases. - -- - -- One might assume that we could get a more accurate result by testing - -- the lower and upper bounds of the type Rst against the bounds of 32-bit - -- Integer. However, there is no easy way to do that. Why? Because in the - -- relatively rare case where this expresion has to be evaluated at run - -- time rather than compile time (when the bounds are dynamic), we need a - -- type to use for the computation. But the possible range of upper bound - -- values for Rst (remembering the possibility of 64-bit modular types) is - -- from -2**63 to 2**64-1, and no run-time type has a big enough range. - - ----------------------- - -- Local Subprograms -- - ----------------------- + subtype Rep_Generator is System.Random_Numbers.Generator; + subtype Rep_State is System.Random_Numbers.State; - function Square_Mod_N (X, N : Int) return Int; - pragma Inline (Square_Mod_N); - -- Computes X**2 mod N avoiding intermediate overflow + function Rep_Random is + new Random_Discrete (Result_Subtype, Result_Subtype'First); - ----------- - -- Image -- - ----------- - - function Image (Of_State : State) return String is + function Random (Gen : Generator) return Result_Subtype is begin - return Int'Image (Of_State.X1) & - ',' & - Int'Image (Of_State.X2) & - ',' & - Int'Image (Of_State.Q); - end Image; - - ------------ - -- Random -- - ------------ - - function Random (Gen : Generator) return Rst is - Genp : constant Pointer := Gen.Gen_State'Unrestricted_Access; - Temp : Int; - TF : Flt; - - begin - -- Check for flat range here, since we are typically run with checks - -- off, note that in practice, this condition will usually be static - -- so we will not actually generate any code for the normal case. - - if Rst'Last < Rst'First then - raise Constraint_Error; - end if; - - -- Continue with computation if non-flat range - - Genp.X1 := Square_Mod_N (Genp.X1, Genp.P); - Genp.X2 := Square_Mod_N (Genp.X2, Genp.Q); - Temp := Genp.X2 - Genp.X1; - - -- Following duplication is not an error, it is a loop unwinding! - - if Temp < 0 then - Temp := Temp + Genp.Q; - end if; - - if Temp < 0 then - Temp := Temp + Genp.Q; - end if; - - TF := Offs + (Flt (Temp) * Flt (Genp.P) + Flt (Genp.X1)) * Genp.Scl; - - -- Pathological, but there do exist cases where the rounding implicit - -- in calculating the scale factor will cause rounding to 'Last + 1. - -- In those cases, returning 'First results in the least bias. - - if TF >= Flt (Rst'Pos (Rst'Last)) + 0.5 then - return Rst'First; - - elsif not Fits_In_32_Bits then - return Rst'Val (Interfaces.Integer_64 (TF)); - - else - return Rst'Val (Int (TF)); - end if; + return Rep_Random (Gen.Rep); end Random; - ----------- - -- Reset -- - ----------- - - procedure Reset (Gen : Generator; Initiator : Integer) is - Genp : constant Pointer := Gen.Gen_State'Unrestricted_Access; - X1, X2 : Int; - - begin - X1 := 2 + Int (Initiator) mod (K1 - 3); - X2 := 2 + Int (Initiator) mod (K2 - 3); - - for J in 1 .. 5 loop - X1 := Square_Mod_N (X1, K1); - X2 := Square_Mod_N (X2, K2); - end loop; - - -- Eliminate effects of small Initiators - - Genp.all := - (X1 => X1, - X2 => X2, - P => K1, - Q => K2, - FP => K1F, - Scl => Scal); - end Reset; - - ----------- - -- Reset -- - ----------- - - procedure Reset (Gen : Generator) is - Genp : constant Pointer := Gen.Gen_State'Unrestricted_Access; - Now : constant Calendar.Time := Calendar.Clock; - X1 : Int; - X2 : Int; - + procedure Reset (Gen : Generator; + Initiator : Integer) is + G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all; begin - X1 := Int (Calendar.Year (Now)) * 12 * 31 + - Int (Calendar.Month (Now) * 31) + - Int (Calendar.Day (Now)); - - X2 := Int (Calendar.Seconds (Now) * Duration (1000.0)); - - X1 := 2 + X1 mod (K1 - 3); - X2 := 2 + X2 mod (K2 - 3); - - -- Eliminate visible effects of same day starts - - for J in 1 .. 5 loop - X1 := Square_Mod_N (X1, K1); - X2 := Square_Mod_N (X2, K2); - end loop; - - Genp.all := - (X1 => X1, - X2 => X2, - P => K1, - Q => K2, - FP => K1F, - Scl => Scal); - + Reset (G, Initiator); end Reset; - ----------- - -- Reset -- - ----------- - - procedure Reset (Gen : Generator; From_State : State) is - Genp : constant Pointer := Gen.Gen_State'Unrestricted_Access; + procedure Reset (Gen : Generator) is + G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all; begin - Genp.all := From_State; + Reset (G); end Reset; - ---------- - -- Save -- - ---------- - - procedure Save (Gen : Generator; To_State : out State) is + procedure Save (Gen : Generator; + To_State : out State) is begin - To_State := Gen.Gen_State; + Save (Gen.Rep, State (To_State)); end Save; - ------------------ - -- Square_Mod_N -- - ------------------ - - function Square_Mod_N (X, N : Int) return Int is + procedure Reset (Gen : Generator; + From_State : State) is + G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all; begin - return Int ((Integer_64 (X) ** 2) mod (Integer_64 (N))); - end Square_Mod_N; + Reset (G, From_State); + end Reset; - ----------- - -- Value -- - ----------- + function Image (Of_State : State) return String is + begin + return Image (Rep_State (Of_State)); + end Image; function Value (Coded_State : String) return State is - Last : constant Natural := Coded_State'Last; - Start : Positive := Coded_State'First; - Stop : Positive := Coded_State'First; - Outs : State; - + G : Generator; + S : Rep_State; begin - while Stop <= Last and then Coded_State (Stop) /= ',' loop - Stop := Stop + 1; - end loop; - - if Stop > Last then - raise Constraint_Error; - end if; - - Outs.X1 := Int'Value (Coded_State (Start .. Stop - 1)); - Start := Stop + 1; - - loop - Stop := Stop + 1; - exit when Stop > Last or else Coded_State (Stop) = ','; - end loop; - - if Stop > Last then - raise Constraint_Error; - end if; - - Outs.X2 := Int'Value (Coded_State (Start .. Stop - 1)); - Outs.Q := Int'Value (Coded_State (Stop + 1 .. Last)); - Outs.P := Outs.Q * 2 + 1; - Outs.FP := Flt (Outs.P); - Outs.Scl := (RstL - RstF + 1.0) / (Flt (Outs.P) * Flt (Outs.Q)); - - -- Now do *some* sanity checks - - if Outs.Q < 31 - or else Outs.X1 not in 2 .. Outs.P - 1 - or else Outs.X2 not in 2 .. Outs.Q - 1 - then - raise Constraint_Error; - end if; - - return Outs; + Reset (G.Rep, Coded_State); + System.Random_Numbers.Save (G.Rep, S); + return State (S); end Value; end Ada.Numerics.Discrete_Random; |