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/*
* randbitrun - check rand bit run lengths of the a55 generator
*
* Copyright (C) 1999 Landon Curt Noll
*
* Calc is open software; you can redistribute it and/or modify it under
* the terms of the version 2.1 of the GNU Lesser General Public License
* as published by the Free Software Foundation.
*
* Calc is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
* Public License for more details.
*
* A copy of version 2.1 of the GNU Lesser General Public License is
* distributed with calc under the filename COPYING-LGPL. You should have
* received a copy with calc; if not, write to Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* Under source code control: 1995/02/13 03:43:11
* File existed as early as: 1995
*
* chongo <was here> /\oo/\ http://www.isthe.com/chongo/
* Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
*/
/*
* We will use randbit(1) to generate a stream if single bits.
* The odds that we will have n bits the same in a row is 1/2^n.
*/
define randbitrun(run_cnt)
{
local i; /* index */
local max_run; /* longest run */
local long_run_cnt; /* number of runs longer than MAX_RUN */
local run; /* current run length */
local tally_sum; /* sum of all tally values */
local last; /* last random number */
local current; /* current random number */
local MAX_RUN = 18; /* max run we will keep track of */
local mat tally[1:MAX_RUN]; /* tally of length of a rise run of 'x' */
local mat prob[1:MAX_RUN]; /* prob[x] = probability of 'x' length run */
/*
* parse args
*/
if (param(0) == 0) {
run_cnt = 65536;
}
/*
* run setup
*/
max_run = 0; /* no runs yet */
long_run_cnt = 0; /* no long runs set */
current = randbit(1); /* our first number */
run = 1;
/*
* compute the run length probabilities
*
* A bit run length of 'r' occurs with a probability of:
*
* 1/2^n;
*/
for (i=1; i <= MAX_RUN; ++i) {
prob[i] = 1.0/(1<<i);
}
/*
* look at a number of random number trials
*/
for (i=0; i < run_cnt; ++i) {
/* get our current number */
last = current;
current = randbit(1);
/* look for a run break */
if (current != last) {
/* record the stats */
if (run > max_run) {
max_run = run;
}
if (run > MAX_RUN) {
++long_run_cnt;
} else {
++tally[run];
}
/* start a new run */
current = randbit(1);
run = 1;
/* note the continuing run */
} else {
++run;
}
}
/* determine the number of runs found */
tally_sum = matsum(tally) + long_run_cnt;
/*
* print the stats
*/
printf("rand runbit test used %d values to produce %d runs\n",
run_cnt, tally_sum);
for (i=1; i <= MAX_RUN; ++i) {
printf("length=%d\tprob=%9.7f\texpect=%d \tcount=%d \terr=%9.7f\n",
i, prob[i], round(tally_sum*prob[i]), tally[i],
(tally[i] - round(tally_sum*prob[i]))/tally_sum);
}
printf("length>%d\t\t\t\t\tcount=%d\n", MAX_RUN, long_run_cnt);
printf("max length=%d\n", max_run);
}