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-rw-r--r--netem/paretonormal.c81
1 files changed, 81 insertions, 0 deletions
diff --git a/netem/paretonormal.c b/netem/paretonormal.c
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+/*
+ * 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;
+}