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Dummy Backend: optimize random-number implementation

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This commit is contained in:
Robin Gareus 2014-07-08 18:16:26 +02:00
parent 941701574e
commit 2d63489196
2 changed files with 30 additions and 21 deletions
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45
libs/backends/dummy/dummy_audiobackend.cc
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@ -1313,9 +1313,6 @@ void DummyAudioPort::setup_generator (GeneratorType const g, float const sampler
{
_gen_type = g;
_rseed = g_get_monotonic_time() % UINT_MAX;
#ifdef COMPILER_MSVC
srand (_rseed);
#endif
switch (_gen_type) {
case PinkNoise:
@ -1325,12 +1322,7 @@ void DummyAudioPort::setup_generator (GeneratorType const g, float const sampler
break;
case SineWave:
{
#ifdef COMPILER_MSVC
const unsigned int rnd = rand ();
#else
const unsigned int rnd = rand_r (&_rseed);
#endif
_tbl_length = 5 + rnd % (int)(samplerate / 20.f);
_tbl_length = 5 + randi() % (int)(samplerate / 20.f);
_wavetable = (Sample*) malloc( _tbl_length * sizeof(Sample));
for (uint32_t i = 0 ; i < _tbl_length; ++i) {
_wavetable[i] = .12589f * sinf(2.0 * M_PI * (float)i / (float)_tbl_length);
@ -1340,14 +1332,29 @@ void DummyAudioPort::setup_generator (GeneratorType const g, float const sampler
}
}
static inline float randf (unsigned int *seedp) {
static const float rmf = RAND_MAX / 2.0;
// TODO this should use a better uniform random generator
#ifdef COMPILER_MSVC
return ((float)rand () / rmf) - 1.f;
inline uint32_t
DummyAudioPort::randi ()
{
// 31bit Park-Miller-Carta Pseudo-Random Number Generator
// http://www.firstpr.com.au/dsp/rand31/
uint32_t hi, lo;
lo = 16807 * (_rseed & 0xffff);
hi = 16807 * (_rseed >> 16);
lo += (hi & 0x7fff) << 16;
lo += hi >> 15;
#if 1
lo = (lo & 0x7fffffff) + (lo >> 31);
#else
return ((float)rand_r (seedp) / rmf) - 1.f;
if (lo > 0x7fffffff) { lo -= 0x7fffffff; }
#endif
return (_rseed = lo);
}
inline float
DummyAudioPort::randf ()
{
return (randi() / 1073741824.f) - 1.f;
}
float DummyAudioPort::grandf ()
@ -1362,8 +1369,8 @@ float DummyAudioPort::grandf ()
}
do {
x1 = randf (&_rseed);
x2 = randf (&_rseed);
x1 = randf ();
x2 = randf ();
r = x1 * x1 + x2 * x2;
} while ((r >= 1.0f) || (r < 1e-22f));
@ -1411,7 +1418,7 @@ void DummyAudioPort::generate (const pframes_t n_samples)
// http://www.musicdsp.org/files/pink.txt
// NB. If 'white' consists of uniform random numbers,
// the pink noise will have an almost gaussian distribution.
const float white = .0498f * randf(&_rseed);
const float white = .0498f * randf ();
_b0 = .99886f * _b0 + white * .0555179f;
_b1 = .99332f * _b1 + white * .0750759f;
_b2 = .96900f * _b2 + white * .1538520f;
@ -1424,7 +1431,7 @@ void DummyAudioPort::generate (const pframes_t n_samples)
break;
case PonyNoise:
for (pframes_t i = 0 ; i < n_samples; ++i) {
const float white = 0.0498f * randf(&_rseed);
const float white = 0.0498f * randf ();
// Paul Kellet's economy method
// http://www.musicdsp.org/files/pink.txt
_b0 = 0.99765 * _b0 + white * 0.0990460;

6
libs/backends/dummy/dummy_audiobackend.h
View File

@ -152,8 +152,10 @@ class DummyAudioPort : public DummyPort {
uint32_t _tbl_length;
uint32_t _tbl_offset;
// (per thread) random seed
unsigned int _rseed;
// random number generator
inline float randf ();
inline uint32_t randi ();
uint32_t _rseed;
// gaussian noise generator
float grandf ();