include/opencascade/math_BullardGenerator.hxx

0001 // Created on: 2014-07-18
0002 // Created by: Alexander Malyshev
0003 // Copyright (c) 2014-2014 OPEN CASCADE SAS
0004 //
0005 // This file is part of Open CASCADE Technology software library.
0006 //
0007 // This library is free software; you can redistribute it and/or modify it under
0008 // the terms of the GNU Lesser General Public License version 2.1 as published
0009 // by the Free Software Foundation, with special exception defined in the file
0010 // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
0011 // distribution for complete text of the license and disclaimer of any warranty.
0012 //
0013 // Alternatively, this file may be used under the terms of Open CASCADE
0014 // commercial license or contractual agreement.
0015
0016 #ifndef _math_BullardGenerator_HeaderFile
0017 #define _math_BullardGenerator_HeaderFile
0018
0019 #include <Standard_Real.hxx>
0020
0021 //! Fast random number generator (the algorithm proposed by Ian C. Bullard).
0022 class math_BullardGenerator
0023 {
0024 public:
0025
0026   //! Creates new Xorshift 64-bit RNG.
0027   math_BullardGenerator (unsigned int theSeed = 1)
0028   : myStateHi (theSeed)
0029   {
0030     SetSeed (theSeed);
0031   }
0032
0033   //! Setup new seed / reset defaults.
0034   void SetSeed (unsigned int theSeed = 1)
0035   {
0036     myStateHi = theSeed;
0037     myStateLo = theSeed ^ 0x49616E42;
0038   }
0039
0040   //! Generates new 64-bit integer value.
0041   unsigned int NextInt()
0042   {
0043     myStateHi = (myStateHi >> 2) + (myStateHi << 2);
0044
0045     myStateHi += myStateLo;
0046     myStateLo += myStateHi;
0047
0048     return myStateHi;
0049   }
0050
0051   //! Generates new floating-point value.
0052   Standard_Real NextReal()
0053   {
0054     return NextInt() / static_cast<Standard_Real> (0xFFFFFFFFu);
0055   }
0056
0057 private:
0058
0059   unsigned int myStateHi;
0060   unsigned int myStateLo;
0061
0062 };
0063
0064 #endif