| 1 |
/* RCSid $Id: pmaprand.h,v 2.7 2016/05/17 17:39:47 rschregle Exp $ */
|
| 2 |
|
| 3 |
/*
|
| 4 |
======================================================================
|
| 5 |
Random number generators for photon distribution
|
| 6 |
|
| 7 |
Roland Schregle (roland.schregle@{hslu.ch, gmail.com})
|
| 8 |
(c) Fraunhofer Institute for Solar Energy Systems,
|
| 9 |
(c) Lucerne University of Applied Sciences and Arts,
|
| 10 |
supported by the Swiss National Science Foundation (SNSF, #147053)
|
| 11 |
======================================================================
|
| 12 |
|
| 13 |
$Id: pmaprand.h,v 2.7 2016/05/17 17:39:47 rschregle Exp $
|
| 14 |
*/
|
| 15 |
|
| 16 |
|
| 17 |
|
| 18 |
#ifndef PMAPRAND_H
|
| 19 |
#define PMAPRAND_H
|
| 20 |
|
| 21 |
/* According to the analytical validation, skipping sequential samples
|
| 22 |
* when sharing a single RNG among multiple sampling domains introduces
|
| 23 |
* overlapping photon rays (reported as 'duplicate keys' when building
|
| 24 |
* the underlying data structure) and therefore bias. This is aggravated
|
| 25 |
* when running parallel photon distribution subprocesses, where photon
|
| 26 |
* rays from different subprocesses may correlate.
|
| 27 |
* We therefore maintain a separate RNG state for each sampling domain
|
| 28 |
* (e.g. photon emission, scattering, and russian roulette). With
|
| 29 |
* multiprocessing, each subprocess has its own instance of the RNG
|
| 30 |
* state, which is independently seeded for decorellation -- see
|
| 31 |
* distribPhotons() and distribPhotonContrib().
|
| 32 |
* The pmapSeed() and pmapRandom() macros below can be adapted to
|
| 33 |
* platform-specific RNGs if necessary. */
|
| 34 |
#if defined(_WIN32) || defined(_WIN64)
|
| 35 |
/* Use standard RNG without state management; the generated sequences
|
| 36 |
* will be suboptimal */
|
| 37 |
#include "random.h"
|
| 38 |
#define pmapSeed(seed, state) srandom(seed)
|
| 39 |
#define pmapRandom(state) frandom()
|
| 40 |
#else
|
| 41 |
/* Assume NIX and manage RNG state via erand48() */
|
| 42 |
#define pmapSeed(seed, state) (state [0] += seed, state [1] += seed, \
|
| 43 |
state [2] += seed)
|
| 44 |
#define pmapRandom(state) erand48(state)
|
| 45 |
#endif
|
| 46 |
|
| 47 |
|
| 48 |
extern unsigned short partState [3], emitState [3], cntState [3],
|
| 49 |
mediumState [3], scatterState [3], rouletteState [3],
|
| 50 |
randSeed;
|
| 51 |
#endif
|
| 52 |
|
