random.h
Go to the documentation of this file.00001 /* 00002 This file is part of the CVD Library. 00003 00004 Copyright (C) 2005 The Authors 00005 00006 This library is free software; you can redistribute it and/or 00007 modify it under the terms of the GNU Lesser General Public 00008 License as published by the Free Software Foundation; either 00009 version 2.1 of the License, or (at your option) any later version. 00010 00011 This library is distributed in the hope that it will be useful, 00012 but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00014 Lesser General Public License for more details. 00015 00016 You should have received a copy of the GNU Lesser General Public 00017 License along with this library; if not, write to the Free Software 00018 Foundation, Inc., 00019 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00020 */ 00021 #ifndef CVD_RANDOM_H 00022 #define CVD_RANDOM_H 00023 00024 #include <cstdlib> 00025 #include <cmath> 00026 00027 namespace CVD { 00032 inline double rand_u() 00033 { 00034 return ((double) std::rand()/ RAND_MAX); 00035 } 00036 00041 inline double rand_g() 00042 { 00043 static bool use_old=false; 00044 static double y2; 00045 double r; 00046 00047 00048 if(!use_old) 00049 { 00050 double x1, x2, w, y1; 00051 do { 00052 x1 = 2.0 * rand_u() - 1.0; 00053 x2 = 2.0 * rand_u() - 1.0; 00054 w = x1 * x1 + x2 * x2; 00055 } while ( w >= 1.0 ); 00056 00057 w = std::sqrt( (-2.0 * std::log( w ) ) / w ); 00058 y1 = x1 * w; 00059 y2 = x2 * w; 00060 00061 r = y1; 00062 use_old = true; 00063 } 00064 else 00065 { 00066 r = y2; 00067 use_old = false; 00068 } 00069 00070 00071 return r; 00072 } 00073 00074 } 00075 00076 #endif