3 # From Tom Phoenix <rootbeer@teleport.com> 22 Feb 1997
4 # Based upon a test script by kgb@ast.cam.ac.uk (Karl Glazebrook)
6 # Looking for the hints? You're in the right place.
7 # The hints are near each test, so search for "TEST #", where
8 # the pound sign is replaced by the number of the test.
10 # I'd like to include some more robust tests, but anything
11 # too subtle to be detected here would require a time-consuming
12 # test. Also, of course, we're here to detect only flaws in Perl;
13 # if there are flaws in the underlying system rand, that's not
14 # our responsibility. But if you want better tests, see
15 # The Art of Computer Programming, Donald E. Knuth, volume 2,
16 # chapter 3. ISBN 0-201-03822-6 (v. 2)
28 my $reps = 10000; # How many times to try rand each time.
29 # May be changed, but should be over 500.
30 # The more the better! (But slower.)
33 # Takes a small integer and returns the number of one-bits in it.
35 my $bits = sprintf "%o", $_[0];
36 while (length $bits) {
37 $total += (0,1,1,2,1,2,2,3)[chop $bits]; # Oct to bits
42 # First, let's see whether randbits is set right
44 my($max, $min, $sum); # Characteristics of rand
45 my($off, $shouldbe); # Problems with randbits
46 my($dev, $bits); # Number of one bits
47 my $randbits = $Config{randbits};
48 $max = $min = rand(1);
51 if ($n < 0.0 or $n >= 1.0) {
53 # WHOA THERE! \$Config{drand01} is set to '$Config{drand01}',
54 # but that apparently produces values < 0.0 or >= 1.0.
55 # Make sure \$Config{drand01} is a valid expression in the
56 # C-language, and produces values in the range [0.0,1.0).
63 $bits += bits($n * 256); # Don't be greedy; 8 is enough
64 # It's too many if randbits is less than 8!
65 # But that should never be the case... I hope.
66 # Note: If you change this, you must adapt the
67 # formula for absolute standard deviation, below.
68 $max = $n if $n > $max;
69 $min = $n if $n < $min;
75 # This test checks for one of Perl's most frequent
76 # mis-configurations. Your system's documentation
77 # for rand(2) should tell you what value you need
78 # for randbits. Usually the diagnostic message
79 # has the right value as well. Just fix it and
80 # recompile, and you'll usually be fine. (The main
81 # reason that the diagnostic message might get the
82 # wrong value is that Config.pm is incorrect.)
84 if ($max <= 0 or $max >= (2 ** $randbits)) {# Just in case...
85 print "# max=[$max] min=[$min]\nnot ok 1\n";
86 print "# This perl was compiled with randbits=$randbits\n";
87 print "# which is _way_ off. Or maybe your system rand is broken,\n";
88 print "# or your C compiler can't multiply, or maybe Martians\n";
89 print "# have taken over your computer. For starters, see about\n";
90 print "# trying a better value for randbits, probably smaller.\n";
91 # If that isn't the problem, we'll have
92 # to put d_martians into Config.pm
93 print "# Skipping remaining tests until randbits is fixed.\n";
97 $off = log($max) / log(2); # log2
98 $off = int($off) + ($off > 0); # Next more positive int
100 $shouldbe = $Config{randbits} + $off;
101 print "# max=[$max] min=[$min]\nnot ok 1\n";
102 print "# This perl was compiled with randbits=$randbits on $^O.\n";
103 print "# Consider using randbits=$shouldbe instead.\n";
104 # And skip the remaining tests; they would be pointless now.
105 print "# Skipping remaining tests until randbits is fixed.\n";
113 # This should always be true: 0 <= rand(1) < 1
114 # If this test is failing, something is seriously wrong,
115 # either in perl or your system's rand function.
117 if ($min < 0 or $max >= 1) { # Slightly redundant...
119 print "# min too low\n" if $min < 0;
120 print "# max too high\n" if $max >= 1;
127 # This is just a crude test. The average number produced
128 # by rand should be about one-half. But once in a while
129 # it will be relatively far away. Note: This test will
130 # occasionally fail on a perfectly good system!
131 # See the hints for test 4 to see why.
134 if ($sum < 0.4 or $sum > 0.6) {
135 print "not ok 3\n# Average random number is far from 0.5\n";
142 # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE
143 # This test will fail .1% of the time on a normal system.
145 # This test asks you to see these hints 100% of the time!
146 # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE
148 # There is probably no reason to be alarmed that
149 # something is wrong with your rand function. But,
150 # if you're curious or if you can't help being
151 # alarmed, keep reading.
153 # This is a less-crude test than test 3. But it has
154 # the same basic flaw: Unusually distributed random
155 # values should occasionally appear in every good
156 # random number sequence. (If you flip a fair coin
157 # twenty times every day, you'll see it land all
158 # heads about one time in a million days, on the
159 # average. That might alarm you if you saw it happen
162 # So, if this test failed on you once, run it a dozen
163 # times. If it keeps failing, it's likely that your
164 # rand is bogus. If it keeps passing, it's likely
165 # that the one failure was bogus. If it's a mix,
166 # read on to see about how to interpret the tests.
168 # The number printed in square brackets is the
169 # standard deviation, a statistical measure
170 # of how unusual rand's behavior seemed. It should
171 # fall in these ranges with these *approximate*
174 # under 1 68.26% of the time
175 # 1-2 27.18% of the time
176 # 2-3 4.30% of the time
177 # over 3 0.26% of the time
179 # If the numbers you see are not scattered approximately
180 # (not exactly!) like that table, check with your vendor
181 # to find out what's wrong with your rand. Or with this
184 # Calculating absoulute standard deviation for number of bits set
185 # (eight bits per rep)
186 $dev = abs ($bits - $reps * 4) / sqrt($reps * 2);
189 print "ok 4\n"; # 95% of the time.
190 print "# Your rand seems fine. If this test failed\n";
191 print "# previously, you may want to run it again.\n";
192 } elsif ($dev < 2.575) {
193 print "ok 4\n# In here about 4% of the time. Hmmm...\n";
194 print "# This is ok, but suspicious. But it will happen\n";
195 print "# one time out of 25, more or less.\n";
196 print "# You should run this test again to be sure.\n";
197 } elsif ($dev < 3.3) {
198 print "ok 4\n# In this range about 1% of the time.\n";
199 print "# This is very suspicious. It will happen only\n";
200 print "# about one time out of 100, more or less.\n";
201 print "# You should run this test again to be sure.\n";
202 } elsif ($dev < 3.9) {
203 print "not ok 4\n# In this range very rarely.\n";
204 print "# This is VERY suspicious. It will happen only\n";
205 print "# about one time out of 1000, more or less.\n";
206 print "# You should run this test again to be sure.\n";
208 print "not ok 4\n# Seriously whacked.\n";
209 print "# This is VERY VERY suspicious.\n";
210 print "# Your rand seems to be bogus.\n";
212 print "#\n# If you are having random number troubles,\n";
213 print "# see the hints within the test script for more\n";
214 printf "# information on why this might fail. [ %.3f ]\n", $dev;
218 srand; # These three lines are for test 7
219 my $time = time; # It's just faster to do them here.
220 my $rand = join ", ", rand, rand, rand;
224 # This test checks that the argument to srand actually
225 # sets the seed for generating random numbers.
232 print "# srand is not consistent.\n";
239 # This test just checks that the previous one didn't
240 # give us false confidence!
244 print "# rand is now unchanging!\n";
251 # This checks that srand without arguments gives
252 # different sequences each time. Note: You shouldn't
253 # be calling srand more than once unless you know
254 # what you're doing! But if this fails on your
255 # system, run perlbug and let the developers know
256 # what other sources of randomness srand should
259 while ($time == time) { } # Wait for new second, just in case.
261 if ((join ", ", rand, rand, rand) eq $rand) {
263 print "# srand without args isn't varying.\n";
269 # Now, let's see whether rand accepts its argument
272 $max = $min = rand(100);
275 $max = $n if $n > $max;
276 $min = $n if $n < $min;
281 # This test checks to see that rand(100) really falls
282 # within the range 0 - 100, and that the numbers produced
283 # have a reasonably-large range among them.
285 if ($min < 0 or $max >= 100 or ($max - $min) < 65) {
287 print "# min too low\n" if $min < 0;
288 print "# max too high\n" if $max >= 100;
289 print "# range too narrow\n" if ($max - $min) < 65;
296 # This test checks that rand without an argument
297 # is equivalent to rand(1).
299 $_ = 12345; # Just for fun.
307 print "# rand without arguments isn't rand(1)!\n";
312 # This checks that rand without an argument is not
313 # rand($_). (In case somebody got overzealous.)
317 print "# rand without arguments isn't under 1!\n";
325 # This test checks whether Perl called srand for you. This should
326 # be the case in version 5.004 and later. Note: You must still
327 # call srand if your code might ever be run on a pre-5.004 system!
331 unless ($Config{d_fork}) {
332 # Skip this test. It's not likely to be system-specific, anyway.
333 print "ok 11\n# Skipping this test on this platform.\n";
339 my $PERL = (($^O eq 'VMS') ? "MCR $^X"
340 : ($^O eq 'MSWin32') ? '.\perl'
341 : ($^O eq 'NetWare') ? 'perl'
343 $pid = open PERL, qq[$PERL -e "print rand"|];
344 die "Couldn't pipe from perl: $!" unless defined $pid;
345 if (defined $first) {
346 if ($first ne <PERL>) {
353 close PERL or die "perl returned error code $?";
355 print "not ok 11\n# srand isn't being autocalled.\n";