netem/normal.c

   1 /*
   2  * Normal distribution table generator
   3  * Taken from the uncopyrighted NISTnet code.
   4  */
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <math.h>
   8 #include <string.h>
   9 #include <limits.h>
  10
  11 #include <linux/types.h>
  12 #include <linux/pkt_sched.h>
  13
  14 #define TABLESIZE 16384
  15 #define TABLEFACTOR NETEM_DIST_SCALE
  16
  17 static double
  18 normal(double x, double mu, double sigma)
  19 {
  20         return .5 + .5*erf((x-mu)/(sqrt(2.0)*sigma));
  21 }
  22
  23
  24 int
  25 main(int argc, char **argv)
  26 {
  27         int i, n;
  28         double x;
  29         double table[TABLESIZE+1];
  30
  31         for (x = -10.0; x < 10.05; x += .00005) {
  32                 i = rint(TABLESIZE * normal(x, 0.0, 1.0));
  33                 table[i] = x;
  34         }
  35
  36
  37         printf("# This is the distribution table for the normal distribution.\n");
  38         for (i = n = 0; i < TABLESIZE; i += 4) {
  39                 int value = (int) rint(table[i]*TABLEFACTOR);
  40                 if (value < SHRT_MIN) value = SHRT_MIN;
  41                 if (value > SHRT_MAX) value = SHRT_MAX;
  42
  43                 printf(" %d", value);
  44                 if (++n == 8) {
  45                         putchar('\n');
  46                         n = 0;
  47                 }
  48         }
  49
  50         return 0;
  51 }