gnu/lib/libg++/g++-include/RNG.h

   1 // This may look like C code, but it is really -*- C++ -*-
   2 /*
   3 Copyright (C) 1988 Free Software Foundation
   4     written by Dirk Grunwald (grunwald@cs.uiuc.edu)
   5
   6 This file is part of GNU CC.
   7
   8 GNU CC is distributed in the hope that it will be useful,
   9 but WITHOUT ANY WARRANTY.  No author or distributor
  10 accepts responsibility to anyone for the consequences of using it
  11 or for whether it serves any particular purpose or works at all,
  12 unless he says so in writing.  Refer to the GNU CC General Public
  13 License for full details.
  14
  15 Everyone is granted permission to copy, modify and redistribute
  16 GNU CC, but only under the conditions described in the
  17 GNU CC General Public License.   A copy of this license is
  18 supposed to have been given to you along with GNU CC so you
  19 can know your rights and responsibilities.  It should be in a
  20 file named COPYING.  Among other things, the copyright notice
  21 and this notice must be preserved on all copies.
  22 */
  23 #ifndef _RNG_h
  24 #define _RNG_h 1
  25 #ifdef __GNUG__
  26 #pragma once
  27 #pragma interface
  28 #endif
  29
  30 #include <assert.h>
  31 #include <math.h>
  32
  33 union PrivateRNGSingleType {                    // used to access floats as unsigneds
  34     float s;
  35     unsigned long u;
  36 };
  37
  38 union PrivateRNGDoubleType {                    // used to access doubles as unsigneds
  39     double d;
  40     unsigned long u[2];
  41 };
  42
  43 //
  44 // Base class for Random Number Generators. See ACG and MLCG for instances.
  45 //
  46 class RNG {
  47     static PrivateRNGSingleType singleMantissa; // mantissa bit vector
  48     static PrivateRNGDoubleType doubleMantissa; // mantissa bit vector
  49 public:
  50     RNG();
  51     //
  52     // Return a long-words word of random bits
  53     //
  54     virtual unsigned long asLong() = 0;
  55     virtual void reset() = 0;
  56     //
  57     // Return random bits converted to either a float or a double
  58     //
  59     float asFloat();
  60     double asDouble();
  61 };
  62
  63 #if defined(__OPTIMIZE__) || defined(USE_LIBGXX_INLINES)
  64
  65
  66 inline float RNG::asFloat()
  67 {
  68     PrivateRNGSingleType result;
  69     result.s = 1.0;
  70     result.u |= (asLong() & singleMantissa.u);
  71     result.s -= 1.0;
  72     assert( result.s < 1.0 && result.s >= 0);
  73     return( result.s );
  74 }
  75
  76 inline double RNG::asDouble()
  77 {
  78     PrivateRNGDoubleType result;
  79     result.d = 1.0;
  80     result.u[0] |= (asLong() & doubleMantissa.u[0]);
  81     result.u[1] |= (asLong() & doubleMantissa.u[1]);
  82     result.d -= 1.0;
  83     assert( result.d < 1.0 && result.d >= 0);
  84     return( result.d );
  85 }
  86
  87 #endif
  88 #endif