llrand.cpp File Reference
Global random generator. More...
#include "linden_common.h"
#include "llrand.h"
#include "lluuid.h"
Go to the source code of this file.
Defines | |
| #define | LL_USE_SYSTEM_RAND 0 |
Functions | |
| static LLRandLagFib2281 | gRandomGenerator (LLUUID::getRandomSeed()) |
| F64 | ll_internal_random_double () |
| F32 | ll_internal_random_float () |
| S32 | ll_rand () |
| Generate a float from [0, RAND_MAX). | |
| S32 | ll_rand (S32 val) |
| Generate a float from [0, val) or (val, 0]. | |
| F32 | ll_frand () |
| Generate a float from [0, 1.0). | |
| F32 | ll_frand (F32 val) |
| Generate a float from [0, val) or (val, 0]. | |
| F64 | ll_drand () |
| Generate a double from [0, 1.0). | |
| F64 | ll_drand (F64 val) |
| Generate a double from [0, val) or (val, 0]. | |
Detailed Description
Global random generator.
- LicenseInfo
- firstyear=2000&license=viewergpl
Copyright (c) 2000-2008, Linden Research, Inc.
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Definition in file llrand.cpp.
Define Documentation
| #define LL_USE_SYSTEM_RAND 0 |
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.
Definition at line 67 of file llrand.cpp.
Function Documentation
| static LLRandLagFib2281 gRandomGenerator | ( | LLUUID:: | getRandomSeed() | ) | [static] |
Referenced by ll_internal_random_double(), and ll_internal_random_float().
Generate a double from [0, val) or (val, 0].
Definition at line 163 of file llrand.cpp.
References ll_internal_random_double().
| F64 ll_drand | ( | ) |
Generate a double from [0, 1.0).
Definition at line 158 of file llrand.cpp.
References ll_internal_random_double().
Generate a float from [0, val) or (val, 0].
Definition at line 143 of file llrand.cpp.
References ll_internal_random_float().
| F32 ll_frand | ( | ) |
Generate a float from [0, 1.0).
Definition at line 138 of file llrand.cpp.
References ll_internal_random_float().
Referenced by LLSkipList< DATA_TYPE, BINARY_DEPTH >::addData(), LLPtrSkipMap< INDEX_T, DATA_T, BINARY_DEPTH >::addData(), LLPtrSkipList< DATA_TYPE, BINARY_DEPTH >::addData(), LLToolPlacer::addObject(), continue_file_receive(), LLAgent::fidget(), LLPtrSkipMap< INDEX_T, DATA_T, BINARY_DEPTH >::getData(), LLVOGrass::initClass(), LLVOWLSky::initStars(), LLCircuitData::LLCircuitData(), LLVOTreeNew::llfrand_signed(), LLVOTreeNew::llfrand_unsigned(), LLEyeMotion::onUpdate(), randomize_sphere(), LLPacketRing::receivePacket(), LLHUDEffectBeam::setupParticle(), LLViewerPartSim::shouldAddPart(), trigger_hippo_bug(), LLViewerPartSourceChat::update(), LLViewerPartSourceSpiral::update(), LLViewerPartSourceScript::update(), LLCloudGroup::updatePuffCount(), LLViewerPartSim::updateSimulation(), LLVOWLSky::updateStarColors(), LLCircuit::updateWatchDogTimers(), and windCallback().
| F64 ll_internal_random_double | ( | ) | [inline] |
Definition at line 105 of file llrand.cpp.
References gRandomGenerator().
Referenced by ll_drand(), and ll_rand().
| F32 ll_internal_random_float | ( | ) | [inline] |
Definition at line 116 of file llrand.cpp.
References gRandomGenerator().
Referenced by ll_frand().
Generate a float from [0, val) or (val, 0].
Definition at line 130 of file llrand.cpp.
References ll_internal_random_double(), and S32.
| S32 ll_rand | ( | ) |
Generate a float from [0, RAND_MAX).
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
Definition at line 125 of file llrand.cpp.
References ll_rand().
Referenced by LLFetchInWelcomeArea::done(), encode_vorbis_file(), LLAgent::fidget(), LLUUID::generate(), get_random_bytes(), LLDir_Solaris::getRandomFileInDir(), LLDir_Linux::getRandomFileInDir(), LLAgent::heardChat(), ll_rand(), LLVOTreeNew::llrand_signed(), lsa_randomize(), random_sort(), LLDoubleLinkedList< DATA_TYPE >::scramble(), LLGestureManager::triggerAndReviseString(), and LLGestureManager::triggerGesture().
