89 lines
2.3 KiB
C
89 lines
2.3 KiB
C
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// This may look like C code, but it is really -*- C++ -*-
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/*
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Copyright (C) 1988 Free Software Foundation
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written by Dirk Grunwald (grunwald@cs.uiuc.edu)
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This file is part of GNU CC.
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GNU CC is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY. No author or distributor
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accepts responsibility to anyone for the consequences of using it
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or for whether it serves any particular purpose or works at all,
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unless he says so in writing. Refer to the GNU CC General Public
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License for full details.
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Everyone is granted permission to copy, modify and redistribute
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GNU CC, but only under the conditions described in the
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GNU CC General Public License. A copy of this license is
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supposed to have been given to you along with GNU CC so you
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can know your rights and responsibilities. It should be in a
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file named COPYING. Among other things, the copyright notice
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and this notice must be preserved on all copies.
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*/
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#ifndef _RNG_h
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#define _RNG_h 1
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#ifdef __GNUG__
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#pragma once
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#pragma interface
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#endif
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#include <assert.h>
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#include <math.h>
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union PrivateRNGSingleType { // used to access floats as unsigneds
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float s;
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unsigned long u;
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};
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union PrivateRNGDoubleType { // used to access doubles as unsigneds
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double d;
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unsigned long u[2];
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};
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//
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// Base class for Random Number Generators. See ACG and MLCG for instances.
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//
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class RNG {
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static PrivateRNGSingleType singleMantissa; // mantissa bit vector
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static PrivateRNGDoubleType doubleMantissa; // mantissa bit vector
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public:
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RNG();
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//
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// Return a long-words word of random bits
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//
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virtual unsigned long asLong() = 0;
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virtual void reset() = 0;
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//
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// Return random bits converted to either a float or a double
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//
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float asFloat();
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double asDouble();
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};
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#if defined(__OPTIMIZE__) || defined(USE_LIBGXX_INLINES)
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inline float RNG::asFloat()
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{
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PrivateRNGSingleType result;
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result.s = 1.0;
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result.u |= (asLong() & singleMantissa.u);
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result.s -= 1.0;
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assert( result.s < 1.0 && result.s >= 0);
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return( result.s );
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}
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inline double RNG::asDouble()
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{
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PrivateRNGDoubleType result;
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result.d = 1.0;
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result.u[0] |= (asLong() & doubleMantissa.u[0]);
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result.u[1] |= (asLong() & doubleMantissa.u[1]);
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result.d -= 1.0;
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assert( result.d < 1.0 && result.d >= 0);
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return( result.d );
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}
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#endif
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#endif
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