+++ /dev/null
-/*
- * 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;
-}
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