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123 lines
3.4 KiB
Plaintext
123 lines
3.4 KiB
Plaintext
/*
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* randombitrun - check rand bit run lengths of random()
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*
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* Copyright (C) 1999 Landon Curt Noll
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*
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* Calc is open software; you can redistribute it and/or modify it under
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* the terms of the version 2.1 of the GNU Lesser General Public License
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* as published by the Free Software Foundation.
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*
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* Calc is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
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* Public License for more details.
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*
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* A copy of version 2.1 of the GNU Lesser General Public License is
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* distributed with calc under the filename COPYING-LGPL. You should have
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* received a copy with calc; if not, write to Free Software Foundation, Inc.
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
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*
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* @(#) $Revision: 29.1 $
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* @(#) $Id: randombitrun.cal,v 29.1 1999/12/14 09:15:32 chongo Exp $
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* @(#) $Source: /usr/local/src/cmd/calc/cal/RCS/randombitrun.cal,v $
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*
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* Under source code control: 1995/02/13 03:43:11
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* File existed as early as: 1995
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*
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* chongo <was here> /\oo/\ http://reality.sgi.com/chongo/
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* Share and enjoy! :-) http://reality.sgi.com/chongo/tech/comp/calc/
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*/
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/*
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* We will use randombit(1) to generate a stream if single bits.
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* The odds that we will have n bits the same in a row is 1/2^n.
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*/
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define randombitrun(run_cnt)
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{
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local i; /* index */
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local max_run; /* longest run */
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local long_run_cnt; /* number of runs longer than MAX_RUN */
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local run; /* current run length */
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local tally_sum; /* sum of all tally values */
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local last; /* last random number */
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local current; /* current random number */
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local MAX_RUN = 18; /* max run we will keep track of */
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local mat tally[1:MAX_RUN]; /* tally of length of a rise run of 'x' */
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local mat prob[1:MAX_RUN]; /* prob[x] = probability of 'x' length run */
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/*
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* parse args
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*/
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if (param(0) == 0) {
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run_cnt = 65536;
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}
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/*
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* run setup
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*/
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max_run = 0; /* no runs yet */
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long_run_cnt = 0; /* no long runs set */
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current = randombit(1); /* our first number */
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run = 1;
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/*
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* compute the run length probabilities
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*
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* A bit run length of 'r' occurs with a probability of:
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*
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* 1/2^n;
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*/
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for (i=1; i <= MAX_RUN; ++i) {
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prob[i] = 1.0/(1<<i);
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}
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/*
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* look at a number of random number trials
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*/
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for (i=0; i < run_cnt; ++i) {
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/* get our current number */
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last = current;
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current = randombit(1);
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/* look for a run break */
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if (current != last) {
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/* record the stats */
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if (run > max_run) {
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max_run = run;
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}
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if (run > MAX_RUN) {
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++long_run_cnt;
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} else {
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++tally[run];
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}
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/* start a new run */
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current = randombit(1);
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run = 1;
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/* note the continuing run */
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} else {
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++run;
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}
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}
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/* determine the number of runs found */
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tally_sum = matsum(tally) + long_run_cnt;
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/*
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* print the stats
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*/
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printf("random runbit test used %d values to produce %d runs\n",
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run_cnt, tally_sum);
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for (i=1; i <= MAX_RUN; ++i) {
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printf("length=%d\tprob=%9.7f\texpect=%d \tcount=%d \terr=%9.7f\n",
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i, prob[i], round(tally_sum*prob[i]), tally[i],
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(tally[i] - round(tally_sum*prob[i]))/tally_sum);
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}
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printf("length>%d\t\t\t\t\tcount=%d\n", MAX_RUN, long_run_cnt);
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printf("max length=%d\n", max_run);
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}
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