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