Commit | Line | Data |
a0d0e21e |
1 | #!./perl |
2 | |
ec761cee |
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 |
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 |
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 |
18 | BEGIN { |
19 | chdir "t" if -d "t"; |
20822f61 |
20 | @INC = '../lib'; |
748a9306 |
21 | } |
748a9306 |
22 | |
ec761cee |
23 | use strict; |
24 | use Config; |
9be67dbc |
25 | use Test::More tests => 8; |
3524d3b9 |
26 | |
ec761cee |
27 | |
2b6bd493 |
28 | my $reps = 10000; # How many times to try rand each time. |
ec761cee |
29 | # May be changed, but should be over 500. |
30 | # The more the better! (But slower.) |
31 | |
32 | sub bits ($) { |
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 | $total; |
a0d0e21e |
40 | } |
41 | |
ec761cee |
42 | # First, let's see whether randbits is set right |
43 | { |
44 | my($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 $n = rand(1); |
ce9935e0 |
51 | if ($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 | } |
ec761cee |
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 < $min; |
70 | } |
71 | |
72 | |
ec761cee |
73 | # This test checks for one of Perl's most frequent |
74 | # mis-configurations. Your system's documentation |
75 | # for rand(2) should tell you what value you need |
76 | # for randbits. Usually the diagnostic message |
77 | # has the right value as well. Just fix it and |
78 | # recompile, and you'll usually be fine. (The main |
79 | # reason that the diagnostic message might get the |
80 | # wrong value is that Config.pm is incorrect.) |
81 | # |
9be67dbc |
82 | unless (ok( !$max <= 0 or $max >= (2 ** $randbits))) {# Just in case... |
83 | print <<DIAG; |
84 | # max=[$max] min=[$min] |
85 | # This perl was compiled with randbits=$randbits |
86 | # which is _way_ off. Or maybe your system rand is broken, |
87 | # or your C compiler can't multiply, or maybe Martians |
88 | # have taken over your computer. For starters, see about |
89 | # trying a better value for randbits, probably smaller. |
90 | DIAG |
91 | |
ec761cee |
92 | # If that isn't the problem, we'll have |
93 | # to put d_martians into Config.pm |
94 | print "# Skipping remaining tests until randbits is fixed.\n"; |
95 | exit; |
96 | } |
97 | |
98 | $off = log($max) / log(2); # log2 |
99 | $off = int($off) + ($off > 0); # Next more positive int |
9be67dbc |
100 | unless (is( $off, 0 )) { |
ec761cee |
101 | $shouldbe = $Config{randbits} + $off; |
9be67dbc |
102 | print "# max=[$max] min=[$min]\n"; |
ec761cee |
103 | print "# This perl was compiled with randbits=$randbits on $^O.\n"; |
104 | print "# Consider using randbits=$shouldbe instead.\n"; |
105 | # And skip the remaining tests; they would be pointless now. |
106 | print "# Skipping remaining tests until randbits is fixed.\n"; |
107 | exit; |
ec761cee |
108 | } |
109 | |
9be67dbc |
110 | |
ec761cee |
111 | # This should always be true: 0 <= rand(1) < 1 |
112 | # If this test is failing, something is seriously wrong, |
113 | # either in perl or your system's rand function. |
114 | # |
9be67dbc |
115 | unless (ok( !($min < 0 or $max >= 1) )) { # Slightly redundant... |
ec761cee |
116 | print "# min too low\n" if $min < 0; |
117 | print "# max too high\n" if $max >= 1; |
ec761cee |
118 | } |
119 | |
9be67dbc |
120 | |
ec761cee |
121 | # This is just a crude test. The average number produced |
122 | # by rand should be about one-half. But once in a while |
123 | # it will be relatively far away. Note: This test will |
124 | # occasionally fail on a perfectly good system! |
125 | # See the hints for test 4 to see why. |
126 | # |
127 | $sum /= $reps; |
9be67dbc |
128 | unless (ok( !($sum < 0.4 or $sum > 0.6) )) { |
129 | print "# Average random number is far from 0.5\n"; |
ec761cee |
130 | } |
a0d0e21e |
131 | |
9be67dbc |
132 | |
ec761cee |
133 | # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE |
134 | # This test will fail .1% of the time on a normal system. |
135 | # also |
136 | # This test asks you to see these hints 100% of the time! |
137 | # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE |
138 | # |
139 | # There is probably no reason to be alarmed that |
140 | # something is wrong with your rand function. But, |
141 | # if you're curious or if you can't help being |
142 | # alarmed, keep reading. |
143 | # |
144 | # This is a less-crude test than test 3. But it has |
145 | # the same basic flaw: Unusually distributed random |
146 | # values should occasionally appear in every good |
147 | # random number sequence. (If you flip a fair coin |
148 | # twenty times every day, you'll see it land all |
149 | # heads about one time in a million days, on the |
150 | # average. That might alarm you if you saw it happen |
151 | # on the first day!) |
152 | # |
153 | # So, if this test failed on you once, run it a dozen |
154 | # times. If it keeps failing, it's likely that your |
155 | # rand is bogus. If it keeps passing, it's likely |
156 | # that the one failure was bogus. If it's a mix, |
157 | # read on to see about how to interpret the tests. |
158 | # |
159 | # The number printed in square brackets is the |
160 | # standard deviation, a statistical measure |
161 | # of how unusual rand's behavior seemed. It should |
162 | # fall in these ranges with these *approximate* |
163 | # probabilities: |
164 | # |
165 | # under 1 68.26% of the time |
166 | # 1-2 27.18% of the time |
167 | # 2-3 4.30% of the time |
168 | # over 3 0.26% of the time |
169 | # |
170 | # If the numbers you see are not scattered approximately |
171 | # (not exactly!) like that table, check with your vendor |
172 | # to find out what's wrong with your rand. Or with this |
173 | # algorithm. :-) |
174 | # |
175 | # Calculating absoulute standard deviation for number of bits set |
176 | # (eight bits per rep) |
177 | $dev = abs ($bits - $reps * 4) / sqrt($reps * 2); |
748a9306 |
178 | |
9be67dbc |
179 | ok( $dev < 3.3 ); |
180 | |
ec761cee |
181 | if ($dev < 1.96) { |
ec761cee |
182 | print "# Your rand seems fine. If this test failed\n"; |
183 | print "# previously, you may want to run it again.\n"; |
184 | } elsif ($dev < 2.575) { |
ec761cee |
185 | print "# This is ok, but suspicious. But it will happen\n"; |
186 | print "# one time out of 25, more or less.\n"; |
187 | print "# You should run this test again to be sure.\n"; |
188 | } elsif ($dev < 3.3) { |
ec761cee |
189 | print "# This is very suspicious. It will happen only\n"; |
190 | print "# about one time out of 100, more or less.\n"; |
191 | print "# You should run this test again to be sure.\n"; |
192 | } elsif ($dev < 3.9) { |
ec761cee |
193 | print "# This is VERY suspicious. It will happen only\n"; |
194 | print "# about one time out of 1000, more or less.\n"; |
195 | print "# You should run this test again to be sure.\n"; |
196 | } else { |
ec761cee |
197 | print "# This is VERY VERY suspicious.\n"; |
198 | print "# Your rand seems to be bogus.\n"; |
199 | } |
200 | print "#\n# If you are having random number troubles,\n"; |
201 | print "# see the hints within the test script for more\n"; |
202 | printf "# information on why this might fail. [ %.3f ]\n", $dev; |
748a9306 |
203 | } |
748a9306 |
204 | |
a0d0e21e |
205 | |
ec761cee |
206 | # Now, let's see whether rand accepts its argument |
207 | { |
208 | my($max, $min); |
209 | $max = $min = rand(100); |
210 | for (1..$reps) { |
211 | my $n = rand(100); |
212 | $max = $n if $n > $max; |
213 | $min = $n if $n < $min; |
214 | } |
215 | |
ec761cee |
216 | # This test checks to see that rand(100) really falls |
217 | # within the range 0 - 100, and that the numbers produced |
218 | # have a reasonably-large range among them. |
219 | # |
9be67dbc |
220 | unless ( ok( !($min < 0 or $max >= 100 or ($max - $min) < 65) ) ) { |
ec761cee |
221 | print "# min too low\n" if $min < 0; |
222 | print "# max too high\n" if $max >= 100; |
223 | print "# range too narrow\n" if ($max - $min) < 65; |
ec761cee |
224 | } |
3524d3b9 |
225 | |
9be67dbc |
226 | |
ec761cee |
227 | # This test checks that rand without an argument |
228 | # is equivalent to rand(1). |
229 | # |
230 | $_ = 12345; # Just for fun. |
231 | srand 12345; |
232 | my $r = rand; |
233 | srand 12345; |
9be67dbc |
234 | is(rand(1), $r, 'rand() without args is rand(1)'); |
235 | |
748a9306 |
236 | |
ec761cee |
237 | # This checks that rand without an argument is not |
238 | # rand($_). (In case somebody got overzealous.) |
239 | # |
9be67dbc |
240 | ok($r < 1, 'rand() without args is under 1'); |
ec761cee |
241 | } |
242 | |