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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) |
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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. |
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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) |
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17 | |
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18 | BEGIN { |
19 | chdir "t" if -d "t"; |
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20 | @INC = '../lib'; |
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21 | } |
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22 | |
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23 | use strict; |
24 | use Config; |
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25 | |
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26 | print "1..11\n"; |
27 | |
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28 | my $reps = 10000; # How many times to try rand each time. |
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29 | # May be changed, but should be over 500. |
30 | # The more the better! (But slower.) |
31 | |
32 | sub bits ($) { |
33 | # Takes a small integer and returns the number of one-bits in it. |
34 | my $total; |
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 |
38 | } |
39 | $total; |
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40 | } |
41 | |
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42 | # First, let's see whether randbits is set right |
43 | { |
44 | my($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 = $min = rand(1); |
49 | for (1..$reps) { |
50 | my $n = rand(1); |
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51 | if ($n < 0.0 or $n >= 1.0) { |
52 | print <<EOM; |
53 | # WHOA THERE! \$Config{drand01} is set to '$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). |
57 | # |
58 | # I give up. |
59 | EOM |
60 | exit; |
61 | } |
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62 | $sum += $n; |
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 < $min; |
70 | } |
71 | |
72 | |
73 | # Hints for TEST 1 |
74 | # |
75 | # This test checks for one of Perl's most frequent |
76 | # mis-configurations. Your system's documentation |
77 | # for rand(2) should tell you what value you need |
78 | # for randbits. Usually the diagnostic message |
79 | # has the right value as well. Just fix it and |
80 | # recompile, and you'll usually be fine. (The main |
81 | # reason that the diagnostic message might get the |
82 | # wrong value is that Config.pm is incorrect.) |
83 | # |
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84 | if ($max <= 0 or $max >= (2 ** $randbits)) {# Just in case... |
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85 | print "# max=[$max] min=[$min]\nnot ok 1\n"; |
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86 | print "# This perl was compiled with randbits=$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"; |
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90 | print "# trying a better value for randbits, probably smaller.\n"; |
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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"; |
94 | exit; |
95 | } |
96 | |
97 | $off = log($max) / log(2); # log2 |
98 | $off = int($off) + ($off > 0); # Next more positive int |
99 | if ($off) { |
100 | $shouldbe = $Config{randbits} + $off; |
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101 | print "# max=[$max] min=[$min]\nnot ok 1\n"; |
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102 | print "# This perl was compiled with randbits=$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"; |
106 | exit; |
107 | } else { |
108 | print "ok 1\n"; |
109 | } |
110 | |
111 | # Hints for TEST 2 |
112 | # |
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. |
116 | # |
117 | if ($min < 0 or $max >= 1) { # Slightly redundant... |
118 | print "not ok 2\n"; |
119 | print "# min too low\n" if $min < 0; |
120 | print "# max too high\n" if $max >= 1; |
121 | } else { |
122 | print "ok 2\n"; |
123 | } |
124 | |
125 | # Hints for TEST 3 |
126 | # |
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. |
132 | # |
133 | $sum /= $reps; |
134 | if ($sum < 0.4 or $sum > 0.6) { |
135 | print "not ok 3\n# Average random number is far from 0.5\n"; |
136 | } else { |
137 | print "ok 3\n"; |
138 | } |
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139 | |
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140 | # Hints for TEST 4 |
141 | # |
142 | # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE |
143 | # This test will fail .1% of the time on a normal system. |
144 | # also |
145 | # This test asks you to see these hints 100% of the time! |
146 | # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE |
147 | # |
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. |
152 | # |
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 |
160 | # on the first day!) |
161 | # |
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. |
167 | # |
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* |
172 | # probabilities: |
173 | # |
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 |
178 | # |
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 |
182 | # algorithm. :-) |
183 | # |
184 | # Calculating absoulute standard deviation for number of bits set |
185 | # (eight bits per rep) |
186 | $dev = abs ($bits - $reps * 4) / sqrt($reps * 2); |
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187 | |
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188 | if ($dev < 1.96) { |
189 | print "ok 4\n"; # 95% of the time. |
190 | print "# Your rand seems fine. If this test failed\n"; |
191 | print "# previously, you may want to run it again.\n"; |
192 | } elsif ($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"; |
207 | } else { |
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"; |
211 | } |
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; |
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215 | } |
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216 | |
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217 | { |
218 | srand; # These three lines are for test 7 |
219 | my $time = time; # It's just faster to do them here. |
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220 | my $rand = join ", ", rand, rand, rand; |
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221 | |
222 | # Hints for TEST 5 |
223 | # |
224 | # This test checks that the argument to srand actually |
225 | # sets the seed for generating random numbers. |
226 | # |
227 | srand(3.14159); |
228 | my $r = rand; |
229 | srand(3.14159); |
230 | if (rand != $r) { |
231 | print "not ok 5\n"; |
232 | print "# srand is not consistent.\n"; |
233 | } else { |
234 | print "ok 5\n"; |
235 | } |
236 | |
237 | # Hints for TEST 6 |
238 | # |
239 | # This test just checks that the previous one didn't |
240 | # give us false confidence! |
241 | # |
242 | if (rand == $r) { |
243 | print "not ok 6\n"; |
244 | print "# rand is now unchanging!\n"; |
245 | } else { |
246 | print "ok 6\n"; |
247 | } |
248 | |
249 | # Hints for TEST 7 |
250 | # |
251 | # This checks that srand without arguments gives |
252 | # different sequences each time. Note: You shouldn't |
253 | # be calling srand more than once unless you know |
254 | # what you're doing! But if this fails on your |
255 | # system, run perlbug and let the developers know |
256 | # what other sources of randomness srand should |
257 | # tap into. |
258 | # |
259 | while ($time == time) { } # Wait for new second, just in case. |
260 | srand; |
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261 | if ((join ", ", rand, rand, rand) eq $rand) { |
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262 | print "not ok 7\n"; |
263 | print "# srand without args isn't varying.\n"; |
264 | } else { |
265 | print "ok 7\n"; |
266 | } |
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267 | } |
268 | |
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269 | # Now, let's see whether rand accepts its argument |
270 | { |
271 | my($max, $min); |
272 | $max = $min = rand(100); |
273 | for (1..$reps) { |
274 | my $n = rand(100); |
275 | $max = $n if $n > $max; |
276 | $min = $n if $n < $min; |
277 | } |
278 | |
279 | # Hints for TEST 8 |
280 | # |
281 | # This test checks to see that rand(100) really falls |
282 | # within the range 0 - 100, and that the numbers produced |
283 | # have a reasonably-large range among them. |
284 | # |
285 | if ($min < 0 or $max >= 100 or ($max - $min) < 65) { |
286 | print "not ok 8\n"; |
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; |
290 | } else { |
291 | print "ok 8\n"; |
292 | } |
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293 | |
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294 | # Hints for TEST 9 |
295 | # |
296 | # This test checks that rand without an argument |
297 | # is equivalent to rand(1). |
298 | # |
299 | $_ = 12345; # Just for fun. |
300 | srand 12345; |
301 | my $r = rand; |
302 | srand 12345; |
303 | if (rand(1) == $r) { |
304 | print "ok 9\n"; |
305 | } else { |
306 | print "not ok 9\n"; |
307 | print "# rand without arguments isn't rand(1)!\n"; |
308 | } |
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309 | |
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310 | # Hints for TEST 10 |
311 | # |
312 | # This checks that rand without an argument is not |
313 | # rand($_). (In case somebody got overzealous.) |
314 | # |
315 | if ($r >= 1) { |
316 | print "not ok 10\n"; |
317 | print "# rand without arguments isn't under 1!\n"; |
318 | } else { |
319 | print "ok 10\n"; |
320 | } |
321 | } |
322 | |
323 | # Hints for TEST 11 |
324 | # |
325 | # This test checks whether Perl called srand for you. This should |
326 | # be the case in version 5.004 and later. Note: You must still |
327 | # call srand if your code might ever be run on a pre-5.004 system! |
328 | # |
329 | AUTOSRAND: |
330 | { |
331 | unless ($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"; |
334 | last; |
335 | } |
336 | |
337 | my($pid, $first); |
338 | for (1..5) { |
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339 | my $PERL = (($^O eq 'VMS') ? "MCR $^X" |
340 | : ($^O eq 'MSWin32') ? '.\perl' |
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341 | : ($^O eq 'NetWare') ? 'perl' |
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342 | : './perl'); |
343 | $pid = open PERL, qq[$PERL -e "print rand"|]; |
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344 | die "Couldn't pipe from perl: $!" unless defined $pid; |
345 | if (defined $first) { |
346 | if ($first ne <PERL>) { |
347 | print "ok 11\n"; |
348 | last AUTOSRAND; |
349 | } |
350 | } else { |
351 | $first = <PERL>; |
352 | } |
353 | close PERL or die "perl returned error code $?"; |
354 | } |
355 | print "not ok 11\n# srand isn't being autocalled.\n"; |
356 | } |