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1 | #!./perl |
2 | ||
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3 | # From Tom Phoenix <rootbeer@teleport.com> 22 Feb 1997 |
4 | # Based upon a test script by kgb@ast.cam.ac.uk (Karl Glazebrook) | |
a0d0e21e | 5 | |
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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. | |
a0d0e21e | 9 | |
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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) | |
a0d0e21e | 17 | |
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18 | BEGIN { |
19 | chdir "t" if -d "t"; | |
20822f61 | 20 | @INC = '../lib'; |
748a9306 | 21 | } |
748a9306 | 22 | |
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23 | use strict; |
24 | use Config; | |
3524d3b9 | 25 | |
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26 | print "1..11\n"; |
27 | ||
28 | srand; # Shouldn't need this with 5.004... | |
29 | # But I'll include it now and test for | |
30 | # whether we needed it later. | |
31 | ||
32 | my $reps = 1000; # How many times to try rand each time. | |
33 | # May be changed, but should be over 500. | |
34 | # The more the better! (But slower.) | |
35 | ||
36 | sub bits ($) { | |
37 | # Takes a small integer and returns the number of one-bits in it. | |
38 | my $total; | |
39 | my $bits = sprintf "%o", $_[0]; | |
40 | while (length $bits) { | |
41 | $total += (0,1,1,2,1,2,2,3)[chop $bits]; # Oct to bits | |
42 | } | |
43 | $total; | |
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44 | } |
45 | ||
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46 | # First, let's see whether randbits is set right |
47 | { | |
48 | my($max, $min, $sum); # Characteristics of rand | |
49 | my($off, $shouldbe); # Problems with randbits | |
50 | my($dev, $bits); # Number of one bits | |
51 | my $randbits = $Config{randbits}; | |
52 | $max = $min = rand(1); | |
53 | for (1..$reps) { | |
54 | my $n = rand(1); | |
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55 | if ($n < 0.0 or $n >= 1.0) { |
56 | print <<EOM; | |
57 | # WHOA THERE! \$Config{drand01} is set to '$Config{drand01}', | |
58 | # but that apparently produces values < 0.0 or >= 1.0. | |
59 | # Make sure \$Config{drand01} is a valid expression in the | |
60 | # C-language, and produces values in the range [0.0,1.0). | |
61 | # | |
62 | # I give up. | |
63 | EOM | |
64 | exit; | |
65 | } | |
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66 | $sum += $n; |
67 | $bits += bits($n * 256); # Don't be greedy; 8 is enough | |
68 | # It's too many if randbits is less than 8! | |
69 | # But that should never be the case... I hope. | |
70 | # Note: If you change this, you must adapt the | |
71 | # formula for absolute standard deviation, below. | |
72 | $max = $n if $n > $max; | |
73 | $min = $n if $n < $min; | |
74 | } | |
75 | ||
76 | ||
77 | # Hints for TEST 1 | |
78 | # | |
79 | # This test checks for one of Perl's most frequent | |
80 | # mis-configurations. Your system's documentation | |
81 | # for rand(2) should tell you what value you need | |
82 | # for randbits. Usually the diagnostic message | |
83 | # has the right value as well. Just fix it and | |
84 | # recompile, and you'll usually be fine. (The main | |
85 | # reason that the diagnostic message might get the | |
86 | # wrong value is that Config.pm is incorrect.) | |
87 | # | |
4afbaa31 | 88 | if ($max <= 0 or $max >= (2 ** $randbits)) {# Just in case... |
ce9935e0 | 89 | print "# max=[$max] min=[$min]\nnot ok 1\n"; |
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90 | print "# This perl was compiled with randbits=$randbits\n"; |
91 | print "# which is _way_ off. Or maybe your system rand is broken,\n"; | |
92 | print "# or your C compiler can't multiply, or maybe Martians\n"; | |
93 | print "# have taken over your computer. For starters, see about\n"; | |
1e422769 | 94 | print "# trying a better value for randbits, probably smaller.\n"; |
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95 | # If that isn't the problem, we'll have |
96 | # to put d_martians into Config.pm | |
97 | print "# Skipping remaining tests until randbits is fixed.\n"; | |
98 | exit; | |
99 | } | |
100 | ||
101 | $off = log($max) / log(2); # log2 | |
102 | $off = int($off) + ($off > 0); # Next more positive int | |
103 | if ($off) { | |
104 | $shouldbe = $Config{randbits} + $off; | |
ce9935e0 | 105 | print "# max=[$max] min=[$min]\nnot ok 1\n"; |
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106 | print "# This perl was compiled with randbits=$randbits on $^O.\n"; |
107 | print "# Consider using randbits=$shouldbe instead.\n"; | |
108 | # And skip the remaining tests; they would be pointless now. | |
109 | print "# Skipping remaining tests until randbits is fixed.\n"; | |
110 | exit; | |
111 | } else { | |
112 | print "ok 1\n"; | |
113 | } | |
114 | ||
115 | # Hints for TEST 2 | |
116 | # | |
117 | # This should always be true: 0 <= rand(1) < 1 | |
118 | # If this test is failing, something is seriously wrong, | |
119 | # either in perl or your system's rand function. | |
120 | # | |
121 | if ($min < 0 or $max >= 1) { # Slightly redundant... | |
122 | print "not ok 2\n"; | |
123 | print "# min too low\n" if $min < 0; | |
124 | print "# max too high\n" if $max >= 1; | |
125 | } else { | |
126 | print "ok 2\n"; | |
127 | } | |
128 | ||
129 | # Hints for TEST 3 | |
130 | # | |
131 | # This is just a crude test. The average number produced | |
132 | # by rand should be about one-half. But once in a while | |
133 | # it will be relatively far away. Note: This test will | |
134 | # occasionally fail on a perfectly good system! | |
135 | # See the hints for test 4 to see why. | |
136 | # | |
137 | $sum /= $reps; | |
138 | if ($sum < 0.4 or $sum > 0.6) { | |
139 | print "not ok 3\n# Average random number is far from 0.5\n"; | |
140 | } else { | |
141 | print "ok 3\n"; | |
142 | } | |
a0d0e21e | 143 | |
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144 | # Hints for TEST 4 |
145 | # | |
146 | # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE | |
147 | # This test will fail .1% of the time on a normal system. | |
148 | # also | |
149 | # This test asks you to see these hints 100% of the time! | |
150 | # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE | |
151 | # | |
152 | # There is probably no reason to be alarmed that | |
153 | # something is wrong with your rand function. But, | |
154 | # if you're curious or if you can't help being | |
155 | # alarmed, keep reading. | |
156 | # | |
157 | # This is a less-crude test than test 3. But it has | |
158 | # the same basic flaw: Unusually distributed random | |
159 | # values should occasionally appear in every good | |
160 | # random number sequence. (If you flip a fair coin | |
161 | # twenty times every day, you'll see it land all | |
162 | # heads about one time in a million days, on the | |
163 | # average. That might alarm you if you saw it happen | |
164 | # on the first day!) | |
165 | # | |
166 | # So, if this test failed on you once, run it a dozen | |
167 | # times. If it keeps failing, it's likely that your | |
168 | # rand is bogus. If it keeps passing, it's likely | |
169 | # that the one failure was bogus. If it's a mix, | |
170 | # read on to see about how to interpret the tests. | |
171 | # | |
172 | # The number printed in square brackets is the | |
173 | # standard deviation, a statistical measure | |
174 | # of how unusual rand's behavior seemed. It should | |
175 | # fall in these ranges with these *approximate* | |
176 | # probabilities: | |
177 | # | |
178 | # under 1 68.26% of the time | |
179 | # 1-2 27.18% of the time | |
180 | # 2-3 4.30% of the time | |
181 | # over 3 0.26% of the time | |
182 | # | |
183 | # If the numbers you see are not scattered approximately | |
184 | # (not exactly!) like that table, check with your vendor | |
185 | # to find out what's wrong with your rand. Or with this | |
186 | # algorithm. :-) | |
187 | # | |
188 | # Calculating absoulute standard deviation for number of bits set | |
189 | # (eight bits per rep) | |
190 | $dev = abs ($bits - $reps * 4) / sqrt($reps * 2); | |
748a9306 | 191 | |
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192 | if ($dev < 1.96) { |
193 | print "ok 4\n"; # 95% of the time. | |
194 | print "# Your rand seems fine. If this test failed\n"; | |
195 | print "# previously, you may want to run it again.\n"; | |
196 | } elsif ($dev < 2.575) { | |
197 | print "ok 4\n# In here about 4% of the time. Hmmm...\n"; | |
198 | print "# This is ok, but suspicious. But it will happen\n"; | |
199 | print "# one time out of 25, more or less.\n"; | |
200 | print "# You should run this test again to be sure.\n"; | |
201 | } elsif ($dev < 3.3) { | |
202 | print "ok 4\n# In this range about 1% of the time.\n"; | |
203 | print "# This is very suspicious. It will happen only\n"; | |
204 | print "# about one time out of 100, more or less.\n"; | |
205 | print "# You should run this test again to be sure.\n"; | |
206 | } elsif ($dev < 3.9) { | |
207 | print "not ok 4\n# In this range very rarely.\n"; | |
208 | print "# This is VERY suspicious. It will happen only\n"; | |
209 | print "# about one time out of 1000, more or less.\n"; | |
210 | print "# You should run this test again to be sure.\n"; | |
211 | } else { | |
212 | print "not ok 4\n# Seriously whacked.\n"; | |
213 | print "# This is VERY VERY suspicious.\n"; | |
214 | print "# Your rand seems to be bogus.\n"; | |
215 | } | |
216 | print "#\n# If you are having random number troubles,\n"; | |
217 | print "# see the hints within the test script for more\n"; | |
218 | printf "# information on why this might fail. [ %.3f ]\n", $dev; | |
748a9306 | 219 | } |
748a9306 | 220 | |
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221 | { |
222 | srand; # These three lines are for test 7 | |
223 | my $time = time; # It's just faster to do them here. | |
270f084f | 224 | my $rand = join ", ", rand, rand, rand; |
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225 | |
226 | # Hints for TEST 5 | |
227 | # | |
228 | # This test checks that the argument to srand actually | |
229 | # sets the seed for generating random numbers. | |
230 | # | |
231 | srand(3.14159); | |
232 | my $r = rand; | |
233 | srand(3.14159); | |
234 | if (rand != $r) { | |
235 | print "not ok 5\n"; | |
236 | print "# srand is not consistent.\n"; | |
237 | } else { | |
238 | print "ok 5\n"; | |
239 | } | |
240 | ||
241 | # Hints for TEST 6 | |
242 | # | |
243 | # This test just checks that the previous one didn't | |
244 | # give us false confidence! | |
245 | # | |
246 | if (rand == $r) { | |
247 | print "not ok 6\n"; | |
248 | print "# rand is now unchanging!\n"; | |
249 | } else { | |
250 | print "ok 6\n"; | |
251 | } | |
252 | ||
253 | # Hints for TEST 7 | |
254 | # | |
255 | # This checks that srand without arguments gives | |
256 | # different sequences each time. Note: You shouldn't | |
257 | # be calling srand more than once unless you know | |
258 | # what you're doing! But if this fails on your | |
259 | # system, run perlbug and let the developers know | |
260 | # what other sources of randomness srand should | |
261 | # tap into. | |
262 | # | |
263 | while ($time == time) { } # Wait for new second, just in case. | |
264 | srand; | |
270f084f | 265 | if ((join ", ", rand, rand, rand) eq $rand) { |
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266 | print "not ok 7\n"; |
267 | print "# srand without args isn't varying.\n"; | |
268 | } else { | |
269 | print "ok 7\n"; | |
270 | } | |
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271 | } |
272 | ||
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273 | # Now, let's see whether rand accepts its argument |
274 | { | |
275 | my($max, $min); | |
276 | $max = $min = rand(100); | |
277 | for (1..$reps) { | |
278 | my $n = rand(100); | |
279 | $max = $n if $n > $max; | |
280 | $min = $n if $n < $min; | |
281 | } | |
282 | ||
283 | # Hints for TEST 8 | |
284 | # | |
285 | # This test checks to see that rand(100) really falls | |
286 | # within the range 0 - 100, and that the numbers produced | |
287 | # have a reasonably-large range among them. | |
288 | # | |
289 | if ($min < 0 or $max >= 100 or ($max - $min) < 65) { | |
290 | print "not ok 8\n"; | |
291 | print "# min too low\n" if $min < 0; | |
292 | print "# max too high\n" if $max >= 100; | |
293 | print "# range too narrow\n" if ($max - $min) < 65; | |
294 | } else { | |
295 | print "ok 8\n"; | |
296 | } | |
3524d3b9 | 297 | |
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298 | # Hints for TEST 9 |
299 | # | |
300 | # This test checks that rand without an argument | |
301 | # is equivalent to rand(1). | |
302 | # | |
303 | $_ = 12345; # Just for fun. | |
304 | srand 12345; | |
305 | my $r = rand; | |
306 | srand 12345; | |
307 | if (rand(1) == $r) { | |
308 | print "ok 9\n"; | |
309 | } else { | |
310 | print "not ok 9\n"; | |
311 | print "# rand without arguments isn't rand(1)!\n"; | |
312 | } | |
748a9306 | 313 | |
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314 | # Hints for TEST 10 |
315 | # | |
316 | # This checks that rand without an argument is not | |
317 | # rand($_). (In case somebody got overzealous.) | |
318 | # | |
319 | if ($r >= 1) { | |
320 | print "not ok 10\n"; | |
321 | print "# rand without arguments isn't under 1!\n"; | |
322 | } else { | |
323 | print "ok 10\n"; | |
324 | } | |
325 | } | |
326 | ||
327 | # Hints for TEST 11 | |
328 | # | |
329 | # This test checks whether Perl called srand for you. This should | |
330 | # be the case in version 5.004 and later. Note: You must still | |
331 | # call srand if your code might ever be run on a pre-5.004 system! | |
332 | # | |
333 | AUTOSRAND: | |
334 | { | |
335 | unless ($Config{d_fork}) { | |
336 | # Skip this test. It's not likely to be system-specific, anyway. | |
337 | print "ok 11\n# Skipping this test on this platform.\n"; | |
338 | last; | |
339 | } | |
340 | ||
341 | my($pid, $first); | |
342 | for (1..5) { | |
68dc0745 | 343 | my $PERL = (($^O eq 'VMS') ? "MCR $^X" |
344 | : ($^O eq 'MSWin32') ? '.\perl' | |
345 | : './perl'); | |
346 | $pid = open PERL, qq[$PERL -e "print rand"|]; | |
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347 | die "Couldn't pipe from perl: $!" unless defined $pid; |
348 | if (defined $first) { | |
349 | if ($first ne <PERL>) { | |
350 | print "ok 11\n"; | |
351 | last AUTOSRAND; | |
352 | } | |
353 | } else { | |
354 | $first = <PERL>; | |
355 | } | |
356 | close PERL or die "perl returned error code $?"; | |
357 | } | |
358 | print "not ok 11\n# srand isn't being autocalled.\n"; | |
359 | } |