diff options
Diffstat (limited to 'gcc/ada/a-nudira.adb')
| -rw-r--r-- | gcc/ada/a-nudira.adb | 266 |
1 files changed, 266 insertions, 0 deletions
diff --git a/gcc/ada/a-nudira.adb b/gcc/ada/a-nudira.adb new file mode 100644 index 00000000000..b029a981ca4 --- /dev/null +++ b/gcc/ada/a-nudira.adb @@ -0,0 +1,266 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT RUNTIME 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 -- +-- -- +-- B o d y -- +-- -- +-- $Revision: 1.17 $ +-- -- +-- Copyright (C) 1992-1999 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- -- +-- ware Foundation; either version 2, 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. See the GNU General Public License -- +-- for more details. You should have received a copy of the GNU General -- +-- Public License distributed with GNAT; see file COPYING. If not, write -- +-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- +-- MA 02111-1307, USA. -- +-- -- +-- As a special exception, if other files instantiate generics from this -- +-- unit, or you link this unit with other files to produce an executable, -- +-- this unit does not by itself cause the resulting executable to be -- +-- covered by the GNU General Public License. This exception does not -- +-- however invalidate any other reasons why the executable file might be -- +-- covered by the GNU Public License. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- +-- -- +------------------------------------------------------------------------------ + +with Ada.Calendar; +with Interfaces; use Interfaces; + +package body Ada.Numerics.Discrete_Random is + + ------------------------- + -- Implementation Note -- + ------------------------- + + -- The design of this spec is very awkward, as a result of Ada 95 not + -- permitting in-out parameters for function formals (most naturally + -- Generator values would be passed this way). In pure Ada 95, the only + -- solution is to use the heap and pointers, and, to avoid memory leaks, + -- controlled types. + + -- This is awfully heavy, so what we do is to use Unrestricted_Access to + -- 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; + + Need_64 : constant Boolean := Rst'Pos (Rst'Last) > Int'Last; + + ----------------------- + -- Local Subprograms -- + ----------------------- + + function Square_Mod_N (X, N : Int) return Int; + pragma Inline (Square_Mod_N); + -- Computes X**2 mod N avoiding intermediate overflow + + ----------- + -- Image -- + ----------- + + function Image (Of_State : State) return String 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 Need_64 then + return Rst'Val (Interfaces.Integer_64 (TF)); + + else + return Rst'Val (Int (TF)); + end if; + + 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; + + 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); + + end Reset; + + ----------- + -- Reset -- + ----------- + + procedure Reset (Gen : Generator; From_State : State) is + Genp : constant Pointer := Gen.Gen_State'Unrestricted_Access; + + begin + Genp.all := From_State; + end Reset; + + ---------- + -- Save -- + ---------- + + procedure Save (Gen : Generator; To_State : out State) is + begin + To_State := Gen.Gen_State; + end Save; + + ------------------ + -- Square_Mod_N -- + ------------------ + + function Square_Mod_N (X, N : Int) return Int is + begin + return Int ((Integer_64 (X) ** 2) mod (Integer_64 (N))); + end Square_Mod_N; + + ----------- + -- Value -- + ----------- + + function Value (Coded_State : String) return State is + Start : Positive := Coded_State'First; + Stop : Positive := Coded_State'First; + Outs : State; + + begin + while Coded_State (Stop) /= ',' loop + Stop := Stop + 1; + end loop; + + Outs.X1 := Int'Value (Coded_State (Start .. Stop - 1)); + Start := Stop + 1; + + loop + Stop := Stop + 1; + exit when Coded_State (Stop) = ','; + end loop; + + Outs.X2 := Int'Value (Coded_State (Start .. Stop - 1)); + Outs.Q := Int'Value (Coded_State (Stop + 1 .. Coded_State'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; + end Value; + +end Ada.Numerics.Discrete_Random; |