/** * @file llrand.h * @brief Information, functions, and typedefs for randomness. * * $LicenseInfo:firstyear=2000&license=viewerlgpl$ * Second Life Viewer Source Code * Copyright (C) 2010, Linden Research, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; * version 2.1 of the License only. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA * $/LicenseInfo$ */ #ifndef LL_LLRAND_H #define LL_LLRAND_H #include <boost/random/lagged_fibonacci.hpp> #include <boost/random/mersenne_twister.hpp> /** * Use the boost random number generators if you want a stateful * random numbers. If you want more random numbers, use the * c-functions since they will generate faster/better randomness * across the process. * * I tested some of the boost random engines, and picked a good double * generator and a good integer generator. I also took some timings * for them on linux using gcc 3.3.5. The harness also did some other * fairly trivial operations to try to limit compiler optimizations, * so these numbers are only good for relative comparisons. * * usec/inter algorithm * 0.21 boost::minstd_rand0 * 0.039 boost:lagged_fibonacci19937 * 0.036 boost:lagged_fibonacci607 * 0.44 boost::hellekalek1995 * 0.44 boost::ecuyer1988 * 0.042 boost::rand48 * 0.043 boost::mt11213b * 0.028 stdlib random() * 0.05 stdlib lrand48() * 0.034 stdlib rand() * 0.020 the old & lame LLRand */ /** *@brief Generate a float from [0, RAND_MAX). */ S32 LL_COMMON_API ll_rand(); /** *@brief Generate a float from [0, val) or (val, 0]. */ S32 LL_COMMON_API ll_rand(S32 val); /** *@brief Generate a float from [0, 1.0). */ F32 LL_COMMON_API ll_frand(); /** *@brief Generate a float from [0, val) or (val, 0]. */ F32 LL_COMMON_API ll_frand(F32 val); /** *@brief Generate a double from [0, 1.0). */ F64 LL_COMMON_API ll_drand(); /** *@brief Generate a double from [0, val) or (val, 0]. */ F64 LL_COMMON_API ll_drand(F64 val); /** * @brief typedefs for good boost lagged fibonacci. * @see boost::lagged_fibonacci * * These generators will quickly generate doubles. Note the memory * requirements, because they are somewhat high. I chose the smallest * one, and one comparable in speed but higher periodicity without * outrageous memory requirements. * To use: * LLRandLagFib607 foo((U32)time(NULL)); * double bar = foo(); */ typedef boost::lagged_fibonacci607 LLRandLagFib607; /**< * lengh of cycle: 2^32,000 * memory: 607*sizeof(double) (about 5K) */ typedef boost::lagged_fibonacci2281 LLRandLagFib2281; /**< * lengh of cycle: 2^120,000 * memory: 2281*sizeof(double) (about 17K) */ /** * @breif typedefs for a good boost mersenne twister implementation. * @see boost::mersenne_twister * * This fairly quickly generates U32 values * To use: * LLRandMT19937 foo((U32)time(NULL)); * U32 bar = foo(); * * lengh of cycle: 2^19,937-1 * memory: about 2496 bytes */ typedef boost::mt11213b LLRandMT19937; #endif