iproute2/tc/normal.c

/*
 * 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)
{
	double x, *table;
	int i, n;

	table = calloc(sizeof(double), TABLESIZE);
	if (!table) {
		fprintf(stderr, "Not enough memory\n");
		return 1;
	}


	for (x = -10.0; x < 10.05; x += .00005) {
		i = (int)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;
		}
	}
	free(table);
	return 0;
}