#include
#include
/*
* This is a simple random number generator with good quality for audio purposes.
* It consists of two polycounters with opposite rotation direction and different
* periods. The periods are coprime, so the total period is the product of both.
*
* -------------------------------------------------------------------------------------------------
* +-> |31:30:29:28:27:26:25:24:23:22:21:20:19:18:17:16:15:14:13:12:11:10: 9: 8: 7: 6: 5: 4: 3: 2: 1: 0|
* | -------------------------------------------------------------------------------------------------
* | | | | | | |
* | +--+--+--+-XOR-+--------+
* | |
* +--------------------------------------------------------------------------------------+
*
* -------------------------------------------------------------------------------------------------
* |31:30:29:28:27:26:25:24:23:22:21:20:19:18:17:16:15:14:13:12:11:10: 9: 8: 7: 6: 5: 4: 3: 2: 1: 0| <-+
* ------------------------------------------------------------------------------------------------- |
* | | | | |
* +--+----XOR----+--+ |
* | |
* +----------------------------------------------------------------------------------------+
*
*
* The first has an period of 3*5*17*257*65537, the second of 7*47*73*178481,
* which gives a period of 18.410.713.077.675.721.215. The result is the
* XORed values of both generators.
*/
static const unsigned char Parity [256] = { // parity
0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0
};
static uint32_t rnd_r1 = 1;
static uint32_t rnd_r2 = 1;
void
set_seed ( uint32_t seed )
{
rnd_r1 = seed != 0 ? seed : 1; // 0 is a forbidden value which locks the generator
rnd_r2 = 1; // the are several (8389119) forbidden codes. 1 is not one of them
}
uint32_t
random_int ( void )
{
uint32_t t1, t2, t3, t4;
t3 = t1 = rnd_r1; t4 = t2 = rnd_r2; // Parity calculation is done via table lookup, this is also available
t1 &= 0xF5; t2 >>= 25; // on CPUs without parity, can be implemented in C and avoid unpredictable
t1 = Parity [t1]; t2 &= 0x63; // jumps and slow rotate through the carry flag operations.
t1 <<= 31; t2 = Parity [t2];
return (rnd_r1 = (t3 >> 1) | t1 ) ^ (rnd_r2 = (t4 + t4) | t2 );
}
double
Random_Equal ( double mult ) // gives a equal distributed random number
{ // between -2^31*mult and +2^31*mult
return mult * (int32_t) random_int ();
}
double
Random_Normal ( void ) // gives a normal distributed random number
{
return sqrt (-2. * log ( (random_int () + 1) * (1./4294967296.)) ) *
cos ( (2.*M_PI/4294967296.) * random_int () );
}
double
Random_Exponential ( double mult )
{
return -log ( (1. + random_int ()) * (1./4294967296.) );
}
double
Random_Triangular ( double mult )
{
return mult * ((double)(int32_t) random_int () + (double)(int32_t) random_int ());
}
/* end of random.c */