82 lines
1.6 KiB
C
82 lines
1.6 KiB
C
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/*
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* Paretoormal distribution table generator
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*
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* This distribution is simply .25*normal + .75*pareto; a combination
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* which seems to match experimentally observed distributions reasonably
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* well, but is computationally easy to handle.
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* The entries represent a scaled inverse of the cumulative distribution
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* function.
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*
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* Taken from the uncopyrighted NISTnet code.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include <limits.h>
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#include <malloc.h>
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#include <linux/types.h>
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#include <linux/pkt_sched.h>
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#define TABLESIZE 16384
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#define TABLEFACTOR NETEM_DIST_SCALE
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static double
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normal(double x, double mu, double sigma)
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{
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return .5 + .5*erf((x-mu)/(sqrt(2.0)*sigma));
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}
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static const double a=3.0;
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static int
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paretovalue(int i)
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{
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double dvalue;
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i = 65536-4*i;
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dvalue = (double)i/(double)65536;
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dvalue = 1.0/pow(dvalue, 1.0/a);
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dvalue -= 1.5;
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dvalue *= (4.0/3.0)*(double)TABLEFACTOR;
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if (dvalue > 32767)
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dvalue = 32767;
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return (int)rint(dvalue);
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}
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int
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main(int argc, char **argv)
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{
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int i,n;
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double x;
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double table[TABLESIZE+1];
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for (x = -10.0; x < 10.05; x += .00005) {
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i = rint(TABLESIZE*normal(x, 0.0, 1.0));
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table[i] = x;
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}
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printf(
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"# This is the distribution table for the paretonormal distribution.\n"
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);
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for (i = n = 0; i < TABLESIZE; i += 4) {
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int normvalue, parvalue, value;
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normvalue = (int) rint(table[i]*TABLEFACTOR);
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parvalue = paretovalue(i);
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value = (normvalue+3*parvalue)/4;
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if (value < SHRT_MIN) value = SHRT_MIN;
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if (value > SHRT_MAX) value = SHRT_MAX;
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printf(" %d", value);
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if (++n == 8) {
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putchar('\n');
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n = 0;
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}
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}
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return 0;
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}
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