xref: /aosp_15_r20/external/iproute2/netem/normal.c (revision de1e4e894b0c224df933550f0afdecc354b238c4)

/*
 * Normal distribution table generator
 * Taken from the uncopyrighted NISTnet code.
 */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include <limits.h>

#include <linux/types.h>
#include <linux/pkt_sched.h>

#define TABLESIZE 16384
#define TABLEFACTOR NETEM_DIST_SCALE

static double
normal(double x, double mu, double sigma)
{
	return .5 + .5*erf((x-mu)/(sqrt(2.0)*sigma));
}


int
main(int argc, char **argv)
{
	int i, n;
	double x;
	double table[TABLESIZE+1];

	for (x = -10.0; x < 10.05; x += .00005) {
		i = rint(TABLESIZE * normal(x, 0.0, 1.0));
		table[i] = x;
	}


	printf("# This is the distribution table for the normal distribution.\n");
	for (i = n = 0; i < TABLESIZE; i += 4) {
		int value = (int) rint(table[i]*TABLEFACTOR);
		if (value < SHRT_MIN) value = SHRT_MIN;
		if (value > SHRT_MAX) value = SHRT_MAX;

		printf(" %d", value);
		if (++n == 8) {
			putchar('\n');
			n = 0;
		}
	}

	return 0;
}