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
25 static double
normal(double x,double mu,double sigma)26 normal(double x, double mu, double sigma)
27 {
28 return .5 + .5*erf((x-mu)/(sqrt(2.0)*sigma));
29 }
30
31 static const double a=3.0;
32
33 static int
paretovalue(int i)34 paretovalue(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
48 int
main(int argc,char ** argv)49 main(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