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llrand.h 3.56 KiB
/**
* @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