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a0d0e21e LW |
1 | #!./perl |
2 | ||
ec761cee TP |
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 | |
ec761cee TP |
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 | |
ec761cee TP |
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 | |
ec761cee TP |
18 | BEGIN { |
19 | chdir "t" if -d "t"; | |
69026470 | 20 | @INC = qw(. ../lib); |
748a9306 | 21 | } |
748a9306 | 22 | |
ec761cee TP |
23 | use strict; |
24 | use Config; | |
69026470 | 25 | |
1ae3d757 | 26 | require "./test.pl"; |
3be8f094 | 27 | plan(tests => 10); |
3524d3b9 | 28 | |
ec761cee | 29 | |
5b35fc8b | 30 | my $reps = 15000; # How many times to try rand each time. |
ec761cee TP |
31 | # May be changed, but should be over 500. |
32 | # The more the better! (But slower.) | |
33 | ||
34 | sub bits ($) { | |
35 | # Takes a small integer and returns the number of one-bits in it. | |
36 | my $total; | |
37 | my $bits = sprintf "%o", $_[0]; | |
38 | while (length $bits) { | |
39 | $total += (0,1,1,2,1,2,2,3)[chop $bits]; # Oct to bits | |
40 | } | |
41 | $total; | |
a0d0e21e LW |
42 | } |
43 | ||
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44 | # First, let's see whether randbits is set right |
45 | { | |
46 | my($max, $min, $sum); # Characteristics of rand | |
47 | my($off, $shouldbe); # Problems with randbits | |
48 | my($dev, $bits); # Number of one bits | |
49 | my $randbits = $Config{randbits}; | |
50 | $max = $min = rand(1); | |
51 | for (1..$reps) { | |
52 | my $n = rand(1); | |
ce9935e0 GS |
53 | if ($n < 0.0 or $n >= 1.0) { |
54 | print <<EOM; | |
55 | # WHOA THERE! \$Config{drand01} is set to '$Config{drand01}', | |
56 | # but that apparently produces values < 0.0 or >= 1.0. | |
57 | # Make sure \$Config{drand01} is a valid expression in the | |
58 | # C-language, and produces values in the range [0.0,1.0). | |
59 | # | |
60 | # I give up. | |
61 | EOM | |
62 | exit; | |
63 | } | |
ec761cee TP |
64 | $sum += $n; |
65 | $bits += bits($n * 256); # Don't be greedy; 8 is enough | |
66 | # It's too many if randbits is less than 8! | |
67 | # But that should never be the case... I hope. | |
68 | # Note: If you change this, you must adapt the | |
69 | # formula for absolute standard deviation, below. | |
70 | $max = $n if $n > $max; | |
71 | $min = $n if $n < $min; | |
72 | } | |
73 | ||
74 | ||
ec761cee TP |
75 | # This test checks for one of Perl's most frequent |
76 | # mis-configurations. Your system's documentation | |
77 | # for rand(2) should tell you what value you need | |
78 | # for randbits. Usually the diagnostic message | |
79 | # has the right value as well. Just fix it and | |
80 | # recompile, and you'll usually be fine. (The main | |
81 | # reason that the diagnostic message might get the | |
82 | # wrong value is that Config.pm is incorrect.) | |
83 | # | |
9be67dbc MS |
84 | unless (ok( !$max <= 0 or $max >= (2 ** $randbits))) {# Just in case... |
85 | print <<DIAG; | |
86 | # max=[$max] min=[$min] | |
87 | # This perl was compiled with randbits=$randbits | |
88 | # which is _way_ off. Or maybe your system rand is broken, | |
89 | # or your C compiler can't multiply, or maybe Martians | |
90 | # have taken over your computer. For starters, see about | |
91 | # trying a better value for randbits, probably smaller. | |
92 | DIAG | |
93 | ||
ec761cee TP |
94 | # If that isn't the problem, we'll have |
95 | # to put d_martians into Config.pm | |
96 | print "# Skipping remaining tests until randbits is fixed.\n"; | |
97 | exit; | |
98 | } | |
99 | ||
100 | $off = log($max) / log(2); # log2 | |
101 | $off = int($off) + ($off > 0); # Next more positive int | |
9be67dbc | 102 | unless (is( $off, 0 )) { |
ec761cee | 103 | $shouldbe = $Config{randbits} + $off; |
9be67dbc | 104 | print "# max=[$max] min=[$min]\n"; |
ec761cee TP |
105 | print "# This perl was compiled with randbits=$randbits on $^O.\n"; |
106 | print "# Consider using randbits=$shouldbe instead.\n"; | |
107 | # And skip the remaining tests; they would be pointless now. | |
108 | print "# Skipping remaining tests until randbits is fixed.\n"; | |
109 | exit; | |
ec761cee TP |
110 | } |
111 | ||
9be67dbc | 112 | |
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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 | # | |
9be67dbc | 117 | unless (ok( !($min < 0 or $max >= 1) )) { # Slightly redundant... |
ec761cee TP |
118 | print "# min too low\n" if $min < 0; |
119 | print "# max too high\n" if $max >= 1; | |
ec761cee TP |
120 | } |
121 | ||
9be67dbc | 122 | |
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123 | # This is just a crude test. The average number produced |
124 | # by rand should be about one-half. But once in a while | |
125 | # it will be relatively far away. Note: This test will | |
126 | # occasionally fail on a perfectly good system! | |
127 | # See the hints for test 4 to see why. | |
128 | # | |
129 | $sum /= $reps; | |
9be67dbc MS |
130 | unless (ok( !($sum < 0.4 or $sum > 0.6) )) { |
131 | print "# Average random number is far from 0.5\n"; | |
ec761cee | 132 | } |
a0d0e21e | 133 | |
9be67dbc | 134 | |
ec761cee | 135 | # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE |
81b6403e | 136 | # This test will fail .006% of the time on a normal system. |
ec761cee TP |
137 | # also |
138 | # This test asks you to see these hints 100% of the time! | |
139 | # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE | |
140 | # | |
141 | # There is probably no reason to be alarmed that | |
142 | # something is wrong with your rand function. But, | |
143 | # if you're curious or if you can't help being | |
144 | # alarmed, keep reading. | |
145 | # | |
146 | # This is a less-crude test than test 3. But it has | |
147 | # the same basic flaw: Unusually distributed random | |
148 | # values should occasionally appear in every good | |
149 | # random number sequence. (If you flip a fair coin | |
150 | # twenty times every day, you'll see it land all | |
151 | # heads about one time in a million days, on the | |
152 | # average. That might alarm you if you saw it happen | |
153 | # on the first day!) | |
154 | # | |
155 | # So, if this test failed on you once, run it a dozen | |
156 | # times. If it keeps failing, it's likely that your | |
157 | # rand is bogus. If it keeps passing, it's likely | |
158 | # that the one failure was bogus. If it's a mix, | |
159 | # read on to see about how to interpret the tests. | |
160 | # | |
161 | # The number printed in square brackets is the | |
162 | # standard deviation, a statistical measure | |
163 | # of how unusual rand's behavior seemed. It should | |
164 | # fall in these ranges with these *approximate* | |
165 | # probabilities: | |
166 | # | |
167 | # under 1 68.26% of the time | |
168 | # 1-2 27.18% of the time | |
169 | # 2-3 4.30% of the time | |
170 | # over 3 0.26% of the time | |
171 | # | |
172 | # If the numbers you see are not scattered approximately | |
173 | # (not exactly!) like that table, check with your vendor | |
174 | # to find out what's wrong with your rand. Or with this | |
175 | # algorithm. :-) | |
176 | # | |
93f09d7b | 177 | # Calculating absolute standard deviation for number of bits set |
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178 | # (eight bits per rep) |
179 | $dev = abs ($bits - $reps * 4) / sqrt($reps * 2); | |
748a9306 | 180 | |
81b6403e | 181 | ok( $dev < 4.0 ); |
9be67dbc | 182 | |
ec761cee | 183 | if ($dev < 1.96) { |
ec761cee TP |
184 | print "# Your rand seems fine. If this test failed\n"; |
185 | print "# previously, you may want to run it again.\n"; | |
186 | } elsif ($dev < 2.575) { | |
ec761cee TP |
187 | print "# This is ok, but suspicious. But it will happen\n"; |
188 | print "# one time out of 25, more or less.\n"; | |
189 | print "# You should run this test again to be sure.\n"; | |
190 | } elsif ($dev < 3.3) { | |
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191 | print "# This is very suspicious. It will happen only\n"; |
192 | print "# about one time out of 100, more or less.\n"; | |
193 | print "# You should run this test again to be sure.\n"; | |
194 | } elsif ($dev < 3.9) { | |
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195 | print "# This is VERY suspicious. It will happen only\n"; |
196 | print "# about one time out of 1000, more or less.\n"; | |
197 | print "# You should run this test again to be sure.\n"; | |
198 | } else { | |
ec761cee TP |
199 | print "# This is VERY VERY suspicious.\n"; |
200 | print "# Your rand seems to be bogus.\n"; | |
201 | } | |
202 | print "#\n# If you are having random number troubles,\n"; | |
203 | print "# see the hints within the test script for more\n"; | |
204 | printf "# information on why this might fail. [ %.3f ]\n", $dev; | |
748a9306 | 205 | } |
748a9306 | 206 | |
a0d0e21e | 207 | |
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208 | # Now, let's see whether rand accepts its argument |
209 | { | |
210 | my($max, $min); | |
211 | $max = $min = rand(100); | |
212 | for (1..$reps) { | |
213 | my $n = rand(100); | |
214 | $max = $n if $n > $max; | |
215 | $min = $n if $n < $min; | |
216 | } | |
217 | ||
ec761cee TP |
218 | # This test checks to see that rand(100) really falls |
219 | # within the range 0 - 100, and that the numbers produced | |
220 | # have a reasonably-large range among them. | |
221 | # | |
9be67dbc | 222 | unless ( ok( !($min < 0 or $max >= 100 or ($max - $min) < 65) ) ) { |
ec761cee TP |
223 | print "# min too low\n" if $min < 0; |
224 | print "# max too high\n" if $max >= 100; | |
225 | print "# range too narrow\n" if ($max - $min) < 65; | |
ec761cee | 226 | } |
3524d3b9 | 227 | |
9be67dbc | 228 | |
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229 | # This test checks that rand without an argument |
230 | # is equivalent to rand(1). | |
231 | # | |
232 | $_ = 12345; # Just for fun. | |
233 | srand 12345; | |
234 | my $r = rand; | |
235 | srand 12345; | |
9be67dbc MS |
236 | is(rand(1), $r, 'rand() without args is rand(1)'); |
237 | ||
748a9306 | 238 | |
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239 | # This checks that rand without an argument is not |
240 | # rand($_). (In case somebody got overzealous.) | |
241 | # | |
9be67dbc | 242 | ok($r < 1, 'rand() without args is under 1'); |
ec761cee TP |
243 | } |
244 | ||
3be8f094 TC |
245 | { # [perl #115928] use a standard rand() implementation |
246 | srand(1); | |
247 | is(int rand(1000), 41, "our own implementation behaves consistently"); | |
248 | is(int rand(1000), 454, "and still consistently"); | |
249 | } |