WSJT-X/lib/qra/q65/normrnd.c

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2020-10-25 20:10:53 -04:00
// normrnd.c
// functions to generate gaussian distributed numbers
//
// (c) 2016 - Nico Palermo, IV3NWV - Microtelecom Srl, Italy
//
// Credits to Andrea Montefusco - IW0HDV for his help on adapting the sources
// to OSs other than MS Windows
//
// ------------------------------------------------------------------------------
// This file is part of the qracodes project, a Forward Error Control
// encoding/decoding package based on Q-ary RA (Repeat and Accumulate) LDPC codes.
//
// qracodes is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// qracodes is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with qracodes source distribution.
// If not, see <http://www.gnu.org/licenses/>.
#include "normrnd.h"
#if _WIN32 // note the underscore: without it, it's not msdn official!
// Windows (x64 and x86)
#include <windows.h> // required only for GetTickCount(...)
#define K_RAND_MAX UINT_MAX
#elif _SVID_SOURCE || _XOPEN_SOURCE || __unix__ || (defined (__APPLE__) && defined(__MACH__)) /* POSIX or Unix or Apple */
#include <stdlib.h>
#define rand_s(x) (*x)=(unsigned int)lrand48() // returns unsigned integers in the range 0..0x7FFFFFFF
#define K_RAND_MAX 0x7FFFFFFF // that's the max number
// generated by lrand48
#else
#error "No good quality PRNG found"
#endif
// use MS rand_s(...) function
void normrnd_s(float *dst, int nitems, float mean, float stdev)
{
unsigned int r;
float phi=0, u=0;
int set = 0;
while (nitems--)
if (set==1) {
*dst++ = (float)sin(phi)*u*stdev+mean;
set = 0;
}
else {
rand_s((unsigned int*)&r); phi = (M_2PI/(1.0f+K_RAND_MAX))*r;
rand_s((unsigned int*)&r); u = (float)sqrt(-2.0f* log( (1.0f/(1.0f+K_RAND_MAX))*(1.0f+r) ) );
*dst++ = (float)cos(phi)*u*stdev+mean;
set=1;
}
}
/* NOT USED
// use MS rand() function
void normrnd(float *dst, int nitems, float mean, float stdev)
{
float phi=0, u=0;
int set = 0;
while (nitems--)
if (set==1) {
*dst++ = (float)sin(phi)*u*stdev+mean;
set = 0;
}
else {
phi = (M_2PI/(1.0f+RAND_MAX))*rand();
u = (float)sqrt(-2.0f* log( (1.0f/(1.0f+RAND_MAX))*(1.0f+rand()) ) );
*dst++ = (float)cos(phi)*u*stdev+mean;
set=1;
}
}
*/