/*

 * Paretoormal distribution table generator

 *

 * This distribution is simply .25*normal + .75*pareto; a combination

 * which seems to match experimentally observed distributions reasonably

 *  well, but is computationally easy to handle.

 * The entries represent a scaled inverse of the cumulative distribution

 * function.

 *

 * Taken from the uncopyrighted NISTnet code.

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <math.h>

#include <limits.h>

#include <malloc.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));

}

static const double a=3.0;

static int

paretovalue(int i)

{

	double dvalue;

	i = 65536-4*i;

	dvalue = (double)i/(double)65536;

	dvalue = 1.0/pow(dvalue, 1.0/a);

	dvalue -= 1.5;

	dvalue *= (4.0/3.0)*(double)TABLEFACTOR;

	if (dvalue > 32767)

		dvalue = 32767;

	return (int)rint(dvalue);

}

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 paretonormal distribution.\n"

	);

	for (i = n = 0; i < TABLESIZE; i += 4) {

		int normvalue, parvalue, value;

		normvalue = (int) rint(table[i]*TABLEFACTOR);

		parvalue = paretovalue(i);

		value = (normvalue+3*parvalue)/4;

		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;

}