LXR iproute2/netem/paretonormal.c

   1/*
   2 * Paretoormal distribution table generator
   3 *
   4 * This distribution is simply .25*normal + .75*pareto; a combination
   5 * which seems to match experimentally observed distributions reasonably
   6 *  well, but is computationally easy to handle.
   7 * The entries represent a scaled inverse of the cumulative distribution
   8 * function.
   9 *
  10 * Taken from the uncopyrighted NISTnet code.
  11 */
  12#include <stdio.h>
  13#include <stdlib.h>
  14#include <string.h>
  15#include <math.h>
  16#include <limits.h>
  17#include <malloc.h>
  18
  19#include <linux/types.h>
  20#include <linux/pkt_sched.h>
  21
  22#define TABLESIZE       16384
  23#define TABLEFACTOR     NETEM_DIST_SCALE
  24
  25static double
  26normal(double x, double mu, double sigma)
  27{
  28        return .5 + .5*erf((x-mu)/(sqrt(2.0)*sigma));
  29}
  30
  31static const double a=3.0;
  32
  33static int
  34paretovalue(int i)
  35{
  36        double dvalue;
  37
  38        i = 65536-4*i;
  39        dvalue = (double)i/(double)65536;
  40        dvalue = 1.0/pow(dvalue, 1.0/a);
  41        dvalue -= 1.5;
  42        dvalue *= (4.0/3.0)*(double)TABLEFACTOR;
  43        if (dvalue > 32767)
  44                dvalue = 32767;
  45        return (int)rint(dvalue);
  46}
  47
  48int
  49main(int argc, char **argv)
  50{
  51        int i,n;
  52        double x;
  53        double table[TABLESIZE+1];
  54
  55        for (x = -10.0; x < 10.05; x += .00005) {
  56                i = rint(TABLESIZE*normal(x, 0.0, 1.0));
  57                table[i] = x;
  58        }
  59        printf(
  60"# This is the distribution table for the paretonormal distribution.\n"
  61        );
  62
  63        for (i = n = 0; i < TABLESIZE; i += 4) {
  64                int normvalue, parvalue, value;
  65
  66                normvalue = (int) rint(table[i]*TABLEFACTOR);
  67                parvalue = paretovalue(i);
  68
  69                value = (normvalue+3*parvalue)/4;
  70                if (value < SHRT_MIN) value = SHRT_MIN;
  71                if (value > SHRT_MAX) value = SHRT_MAX;
  72
  73                printf(" %d", value);
  74                if (++n == 8) {
  75                        putchar('\n');
  76                        n = 0;
  77                }
  78        }
  79
  80        return 0;
  81}
  82