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Diffstat (limited to 'indra/llcommon/llrand.cpp')
| -rw-r--r-- | indra/llcommon/llrand.cpp | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/indra/llcommon/llrand.cpp b/indra/llcommon/llrand.cpp new file mode 100644 index 0000000000..11ecd8efde --- /dev/null +++ b/indra/llcommon/llrand.cpp @@ -0,0 +1,176 @@ +/** + * @file llrand.cpp + * @brief Global random generator. + * + * $LicenseInfo:firstyear=2000&license=viewergpl$ + * + * Copyright (c) 2000-2007, 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://secondlife.com/developers/opensource/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://secondlife.com/developers/opensource/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. + * $/LicenseInfo$ + */ + +#include "linden_common.h" + +#include "llrand.h" +#include "lluuid.h" + +/** + * Through analysis, we have decided that we want to take values which + * are close enough to 1.0 to map back to 0.0. We came to this + * conclusion from noting that: + * + * [0.0, 1.0) + * + * when scaled to the integer set: + * + * [0, 4) + * + * there is some value close enough to 1.0 that when multiplying by 4, + * gets truncated to 4. Therefore: + * + * [0,1-eps] => 0 + * [1,2-eps] => 1 + * [2,3-eps] => 2 + * [3,4-eps] => 3 + * + * So 0 gets uneven distribution if we simply clamp. The actual + * clamp utilized in this file is to map values out of range back + * to 0 to restore uniform distribution. + * + * Also, for clamping floats when asking for a distribution from + * [0.0,g) we have determined that for values of g < 0.5, then + * rand*g=g, which is not the desired result. As above, we clamp to 0 + * to restore uniform distribution. + */ + +// *NOTE: The system rand implementation is probably not correct. +#define LL_USE_SYSTEM_RAND 0 + +#if LL_USE_SYSTEM_RAND +#include <cstdlib> +#endif + +#if LL_USE_SYSTEM_RAND +class LLSeedRand +{ +public: + LLSeedRand() + { +#if LL_WINDOWS + srand(LLUUID::getRandomSeed()); +#else + srand48(LLUUID::getRandomSeed()); +#endif + } +}; +static LLSeedRand sRandomSeeder; +inline F64 ll_internal_random_double() +{ +#if LL_WINDOWS + return (F64)rand() / (F64)RAND_MAX; +#else + return drand48(); +#endif +} +inline F32 ll_internal_random_float() +{ +#if LL_WINDOWS + return (F32)rand() / (F32)RAND_MAX; +#else + return (F32)drand48(); +#endif +} +#else +static LLRandLagFib2281 gRandomGenerator(LLUUID::getRandomSeed()); +inline F64 ll_internal_random_double() +{ + // *HACK: Through experimentation, we have found that dual core + // CPUs (or at least multi-threaded processes) seem to + // occasionally give an obviously incorrect random number -- like + // 5^15 or something. Sooooo, clamp it as described above. + F64 rv = gRandomGenerator(); + if(!((rv >= 0.0) && (rv < 1.0))) return fmod(rv, 1.0); + return rv; +} + +inline F32 ll_internal_random_float() +{ + // The clamping rules are described above. + F32 rv = (F32)gRandomGenerator(); + if(!((rv >= 0.0f) && (rv < 1.0f))) return fmod(rv, 1.f); + return rv; +} +#endif + +S32 ll_rand() +{ + return ll_rand(RAND_MAX); +} + +S32 ll_rand(S32 val) +{ + // The clamping rules are described above. + S32 rv = (S32)(ll_internal_random_double() * val); + if(rv == val) return 0; + return rv; +} + +F32 ll_frand() +{ + return ll_internal_random_float(); +} + +F32 ll_frand(F32 val) +{ + // The clamping rules are described above. + F32 rv = ll_internal_random_float() * val; + if(val > 0) + { + if(rv >= val) return 0.0f; + } + else + { + if(rv <= val) return 0.0f; + } + return rv; +} + +F64 ll_drand() +{ + return ll_internal_random_double(); +} + +F64 ll_drand(F64 val) +{ + // The clamping rules are described above. + F64 rv = ll_internal_random_double() * val; + if(val > 0) + { + if(rv >= val) return 0.0; + } + else + { + if(rv <= val) return 0.0; + } + return rv; +} |