Rename: tc/maketable.c -> netem/maketable.c

(Logical change 1.141)

netem/maketable.c

+/*
+ * Experimental data  distribution table generator
+ * Taken from the uncopyrighted NISTnet code.
+ *
+ * Rread in a series of "random" data values, either
+ * experimentally or generated from some probability distribution.
+ * From this, create the inverse distribution table used to approximate
+ * the distribution.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <malloc.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+
+double *
+readdoubles(FILE *fp, int *number)
+{
+	struct stat info;
+	double *x;
+	int limit;
+	int n=0, i;
+
+	fstat(fileno(fp), &info);
+	if (info.st_size > 0) {
+		limit = 2*info.st_size/sizeof(double);	/* @@ approximate */
+	} else {
+		limit = 10000;
+	}
+
+	x = calloc(limit, sizeof(double));
+	if (!x) {
+		perror("double alloc");
+		exit(3);
+	}
+
+	for (i=0; i<limit; ++i){
+		fscanf(fp, "%lf", &x[i]);
+		if (feof(fp))
+			break;
+		++n;
+	}
+	*number = n;
+	return x;
+}
+
+void
+arraystats(double *x, int limit, double *mu, double *sigma, double *rho)
+{
+	int n=0, i;
+	double sumsquare=0.0, sum=0.0, top=0.0;
+	double sigma2=0.0;
+
+	for (i=0; i<limit; ++i){
+		sumsquare += x[i]*x[i];
+		sum += x[i];
+		++n;
+	}
+	*mu = sum/(double)n;
+	*sigma = sqrt((sumsquare - (double)n*(*mu)*(*mu))/(double)(n-1));
+
+	for (i=1; i < n; ++i){
+		top += ((double)x[i]- *mu)*((double)x[i-1]- *mu);
+		sigma2 += ((double)x[i-1] - *mu)*((double)x[i-1] - *mu);
+
+	}
+	*rho = top/sigma2;
+}
+
+/* Create a (normalized) distribution table from a set of observed
+ * values.  The table is fixed to run from (as it happens) -4 to +4,
+ * with granularity .00002.
+ */
+
+#define TABLESIZE	16384/4
+#define TABLEFACTOR	8192
+#ifndef MINSHORT
+#define MINSHORT	-32768
+#define MAXSHORT	32767
+#endif
+
+/* Since entries in the inverse are scaled by TABLEFACTOR, and can't be bigger
+ * than MAXSHORT, we don't bother looking at a larger domain than this:
+ */
+#define DISTTABLEDOMAIN ((MAXSHORT/TABLEFACTOR)+1)
+#define DISTTABLEGRANULARITY 50000
+#define DISTTABLESIZE (DISTTABLEDOMAIN*DISTTABLEGRANULARITY*2)
+
+static int *
+makedist(double *x, int limit, double mu, double sigma)
+{
+	int *table;
+	int i, index, first=DISTTABLESIZE, last=0;
+	double input;
+
+	table = calloc(DISTTABLESIZE, sizeof(int));
+	if (!table) {
+		perror("table alloc");
+		exit(3);
+	}
+
+	for (i=0; i < limit; ++i) {
+		/* Normalize value */
+		input = (x[i]-mu)/sigma;
+
+		index = (int)rint((input+DISTTABLEDOMAIN)*DISTTABLEGRANULARITY);
+		if (index < 0) index = 0;
+		if (index >= DISTTABLESIZE) index = DISTTABLESIZE-1;
+		++table[index];
+		if (index > last)
+			last = index +1;
+		if (index < first)
+			first = index;
+	}
+	return table;
+}
+
+/* replace an array by its cumulative distribution */
+static void
+cumulativedist(int *table, int limit, int *total)
+{
+	int accum=0;
+
+	while (--limit >= 0) {
+		accum += *table;
+		*table++ = accum;
+	}
+	*total = accum;
+}
+
+static short *
+inverttable(int *table, int inversesize, int tablesize, int cumulative)
+{
+	int i, inverseindex, inversevalue;
+	short *inverse;
+	double findex, fvalue;
+
+	inverse = (short *)malloc(inversesize*sizeof(short));
+	for (i=0; i < inversesize; ++i) {
+		inverse[i] = MINSHORT;
+	}
+	for (i=0; i < tablesize; ++i) {
+		findex = ((double)i/(double)DISTTABLEGRANULARITY) - DISTTABLEDOMAIN;
+		fvalue = (double)table[i]/(double)cumulative;
+		inverseindex = (int)rint(fvalue*inversesize);
+		inversevalue = (int)rint(findex*TABLEFACTOR);
+		if (inversevalue <= MINSHORT) inversevalue = MINSHORT+1;
+		if (inversevalue > MAXSHORT) inversevalue = MAXSHORT;
+		inverse[inverseindex] = inversevalue;
+	}
+	return inverse;
+
+}
+
+/* Run simple linear interpolation over the table to fill in missing entries */
+static void
+interpolatetable(short *table, int limit)
+{
+	int i, j, last, lasti = -1;
+
+	last = MINSHORT;
+	for (i=0; i < limit; ++i) {
+		if (table[i] == MINSHORT) {
+			for (j=i; j < limit; ++j)
+				if (table[j] != MINSHORT)
+					break;
+			if (j < limit) {
+				table[i] = last + (i-lasti)*(table[j]-last)/(j-lasti);
+			} else {
+				table[i] = last + (i-lasti)*(MAXSHORT-last)/(limit-lasti);
+			}
+		} else {
+			last = table[i];
+			lasti = i;
+		}
+	}
+}
+
+static void
+printtable(const short *table, int limit)
+{
+	int i;
+
+	printf("# This is the distribution table for the experimental distribution.\n");
+
+	for (i=0 ; i < limit; ++i) {
+		printf("%d%c", table[i],
+		       (i % 8) == 7 ? '\n' : ' ');
+	}
+}
+
+int 
+main(int argc, char **argv)
+{
+	FILE *fp;
+	double *x;
+	double mu, sigma, rho;
+	int limit;
+	int *table;
+	short *inverse;
+	int total;
+
+	if (argc > 1) {
+		if (!(fp = fopen(argv[1], "r"))) {
+			perror(argv[1]);
+			exit(1);
+		}
+	} else {
+		fp = stdin;
+	}				
+	x = readdoubles(fp, &limit);
+	if (limit <= 0) {
+		fprintf(stderr, "Nothing much read!\n");
+		exit(2);
+	}
+	arraystats(x, limit, &mu, &sigma, &rho);
+#ifdef DEBUG
+	fprintf(stderr, "%d values, mu %10.4f, sigma %10.4f, rho %10.4f\n",
+		limit, mu, sigma, rho);
+#endif
+	
+	table = makedist(x, limit, mu, sigma);
+	free((void *) x);
+	cumulativedist(table, DISTTABLESIZE, &total);
+	inverse = inverttable(table, TABLESIZE, DISTTABLESIZE, total);
+	interpolatetable(inverse, TABLESIZE);
+	printtable(inverse, TABLESIZE);
+	return 0;
+}