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/**
* @file llrand.h
* @brief Information, functions, and typedefs for randomness.
*
* $LicenseInfo:firstyear=2000&license=viewergpl$
*
* Copyright (c) 2000-2009, Linden Research, Inc.
*
* Second Life Viewer Source Code
* The source code in this file ("Source Code") is provided by Linden Lab
* to you under the terms of the GNU General Public License, version 2.0
* ("GPL"), unless you have obtained a separate licensing agreement
* ("Other License"), formally executed by you and Linden Lab. Terms of
* the GPL can be found in doc/GPL-license.txt in this distribution, or
* online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
*
* There are special exceptions to the terms and conditions of the GPL as
* it is applied to this Source Code. View the full text of the exception
* in the file doc/FLOSS-exception.txt in this software distribution, or
* online at
* http://secondlifegrid.net/programs/open_source/licensing/flossexception
*
* By copying, modifying or distributing this software, you acknowledge
* that you have read and understood your obligations described above,
* and agree to abide by those obligations.
*
* ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
* WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
* COMPLETENESS OR PERFORMANCE.
* $/LicenseInfo$
*/
#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_rand();
/**
*@brief Generate a float from [0, val) or (val, 0].
*/
S32 ll_rand(S32 val);
/**
*@brief Generate a float from [0, 1.0).
*/
F32 ll_frand();
/**
*@brief Generate a float from [0, val) or (val, 0].
*/
F32 ll_frand(F32 val);
/**
*@brief Generate a double from [0, 1.0).
*/
F64 ll_drand();
/**
*@brief Generate a double from [0, val) or (val, 0].
*/
F64 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
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