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Applying Seth's patch from #265 adding entropy BiFs.

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Robin Sommer 2011-01-06 17:16:10 -08:00
parent 5d41794034
commit dbca5be43c
6 changed files with 423 additions and 4 deletions
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256
src/RandTest.cc Normal file
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/*
Apply various randomness tests to a stream of bytes
by John Walker -- September 1996
http://www.fourmilab.ch/
Modified for Bro by Seth Hall - July 2010
*/
#include <RandTest.h>
RandTest::RandTest()
{
totalc = 0;
mp = 0;
sccfirst = 1;
inmont = mcount = 0;
cexp = montex = montey = montepi = sccu0 = scclast = scct1 = scct2 = scct3 = 0.0;
for (int i = 0; i < 256; i++)
{
ccount[i] = 0;
}
}
void RandTest::add(void *buf, int bufl)
{
unsigned char *bp = (unsigned char*)buf;
int oc;
while (bufl-- > 0)
{
oc = *bp++;
ccount[oc]++; /* Update counter for this bin */
totalc++;
/* Update inside / outside circle counts for Monte Carlo
computation of PI */
monte[mp++] = oc; /* Save character for Monte Carlo */
if (mp >= RT_MONTEN) /* Calculate every RT_MONTEN character */
{
mp = 0;
mcount++;
montex = 0;
montey = 0;
for (int mj=0; mj < RT_MONTEN/2; mj++)
{
montex = (montex * 256.0) + monte[mj];
montey = (montey * 256.0) + monte[(RT_MONTEN / 2) + mj];
}
if (montex*montex + montey*montey <= RT_INCIRC)
{
inmont++;
}
}
/* Update calculation of serial correlation coefficient */
if (sccfirst)
{
sccfirst = 0;
scclast = 0;
sccu0 = oc;
}
else
{
scct1 = scct1 + scclast * oc;
}
scct2 = scct2 + oc;
scct3 = scct3 + (oc * oc);
scclast = oc;
oc <<= 1;
}
}
void RandTest::end(double *r_ent, double *r_chisq,
double *r_mean, double *r_montepicalc, double *r_scc)
{
int i;
double ent, chisq, scc, datasum;
ent = 0.0; chisq = 0.0; scc = 0.0; datasum = 0.0;
double prob[256]; /* Probabilities per bin for entropy */
/* Complete calculation of serial correlation coefficient */
scct1 = scct1 + scclast * sccu0;
scct2 = scct2 * scct2;
scc = totalc * scct3 - scct2;
if (scc == 0.0)
scc = -100000;
else
scc = (totalc * scct1 - scct2) / scc;
/* Scan bins and calculate probability for each bin and
Chi-Square distribution. The probability will be reused
in the entropy calculation below. While we're at it,
we sum of all the data which will be used to compute the
mean. */
cexp = totalc / 256.0; /* Expected count per bin */
for (i = 0; i < 256; i++)
{
double a = ccount[i] - cexp;
prob[i] = ((double) ccount[i]) / totalc;
chisq += (a * a) / cexp;
datasum += ((double) i) * ccount[i];
}
/* Calculate entropy */
for (i = 0; i < 256; i++)
{
if (prob[i] > 0.0)
{
ent += prob[i] * rt_log2(1 / prob[i]);
}
}
/* Calculate Monte Carlo value for PI from percentage of hits
within the circle */
montepi = 4.0 * (((double) inmont) / mcount);
/* Return results through arguments */
*r_ent = ent;
*r_chisq = chisq;
*r_mean = datasum / totalc;
*r_montepicalc = montepi;
*r_scc = scc;
}
/*
Apply various randomness tests to a stream of bytes
by John Walker -- September 1996
http://www.fourmilab.ch/
Modified for Bro by Seth Hall - July 2010
*/
#include <RandTest.h>
RandTest::RandTest()
{
totalc = 0;
mp = 0;
sccfirst = 1;
inmont = mcount = 0;
cexp = montex = montey = montepi = sccu0 = scclast = scct1 = scct2 = scct3 = 0.0;
for (int i = 0; i < 256; i++)
{
ccount[i] = 0;
}
}
void RandTest::add(void *buf, int bufl)
{
unsigned char *bp = (unsigned char*)buf;
int oc;
while (bufl-- > 0)
{
oc = *bp++;
ccount[oc]++; /* Update counter for this bin */
totalc++;
/* Update inside / outside circle counts for Monte Carlo
computation of PI */
monte[mp++] = oc; /* Save character for Monte Carlo */
if (mp >= RT_MONTEN) /* Calculate every RT_MONTEN character */
{
mp = 0;
mcount++;
montex = 0;
montey = 0;
for (int mj=0; mj < RT_MONTEN/2; mj++)
{
montex = (montex * 256.0) + monte[mj];
montey = (montey * 256.0) + monte[(RT_MONTEN / 2) + mj];
}
if (montex*montex + montey*montey <= RT_INCIRC)
{
inmont++;
}
}
/* Update calculation of serial correlation coefficient */
if (sccfirst)
{
sccfirst = 0;
scclast = 0;
sccu0 = oc;
}
else
{
scct1 = scct1 + scclast * oc;
}
scct2 = scct2 + oc;
scct3 = scct3 + (oc * oc);
scclast = oc;
oc <<= 1;
}
}
void RandTest::end(double *r_ent, double *r_chisq,
double *r_mean, double *r_montepicalc, double *r_scc)
{
int i;
double ent, chisq, scc, datasum;
ent = 0.0; chisq = 0.0; scc = 0.0; datasum = 0.0;
double prob[256]; /* Probabilities per bin for entropy */
/* Complete calculation of serial correlation coefficient */
scct1 = scct1 + scclast * sccu0;
scct2 = scct2 * scct2;
scc = totalc * scct3 - scct2;
if (scc == 0.0)
scc = -100000;
else
scc = (totalc * scct1 - scct2) / scc;
/* Scan bins and calculate probability for each bin and
Chi-Square distribution. The probability will be reused
in the entropy calculation below. While we're at it,
we sum of all the data which will be used to compute the
mean. */
cexp = totalc / 256.0; /* Expected count per bin */
for (i = 0; i < 256; i++)
{
double a = ccount[i] - cexp;
prob[i] = ((double) ccount[i]) / totalc;
chisq += (a * a) / cexp;
datasum += ((double) i) * ccount[i];
}
/* Calculate entropy */
for (i = 0; i < 256; i++)
{
if (prob[i] > 0.0)
{
ent += prob[i] * rt_log2(1 / prob[i]);
}
}
/* Calculate Monte Carlo value for PI from percentage of hits
within the circle */
montepi = 4.0 * (((double) inmont) / mcount);
/* Return results through arguments */
*r_ent = ent;
*r_chisq = chisq;
*r_mean = datasum / totalc;
*r_montepicalc = montepi;
*r_scc = scc;
}