#!./perl
-#From jhi@snakemail.hut.fi Mon May 16 10:36:46 1994
-#Date: Sun, 15 May 1994 20:39:09 +0300
-#From: Jarkko Hietaniemi <jhi@snakemail.hut.fi>
+# From Tom Phoenix <rootbeer@teleport.com> 22 Feb 1997
+# Based upon a test script by kgb@ast.cam.ac.uk (Karl Glazebrook)
-print "1..2\n";
+# Looking for the hints? You're in the right place.
+# The hints are near each test, so search for "TEST #", where
+# the pound sign is replaced by the number of the test.
-$n = 1000;
+# I'd like to include some more robust tests, but anything
+# too subtle to be detected here would require a time-consuming
+# test. Also, of course, we're here to detect only flaws in Perl;
+# if there are flaws in the underlying system rand, that's not
+# our responsibility. But if you want better tests, see
+# The Art of Computer Programming, Donald E. Knuth, volume 2,
+# chapter 3. ISBN 0-201-03822-6 (v. 2)
-$c = 0;
-for (1..$n) {
- last if (rand() > 1 || rand() < 0);
- $c++;
+BEGIN {
+ chdir "t" if -d "t";
+ @INC = '../lib';
}
-if ($c == $n) {print "ok 1\n";} else {print "not ok 1\n"}
+use strict;
+use Config;
-$c = 0;
-for (1..$n) {
- last if (rand(10) > 10 || rand(10) < 0);
- $c++;
+print "1..11\n";
+
+srand; # Shouldn't need this with 5.004...
+ # But I'll include it now and test for
+ # whether we needed it later.
+
+my $reps = 1000; # How many times to try rand each time.
+ # May be changed, but should be over 500.
+ # The more the better! (But slower.)
+
+sub bits ($) {
+ # Takes a small integer and returns the number of one-bits in it.
+ my $total;
+ my $bits = sprintf "%o", $_[0];
+ while (length $bits) {
+ $total += (0,1,1,2,1,2,2,3)[chop $bits]; # Oct to bits
+ }
+ $total;
+}
+
+# First, let's see whether randbits is set right
+{
+ my($max, $min, $sum); # Characteristics of rand
+ my($off, $shouldbe); # Problems with randbits
+ my($dev, $bits); # Number of one bits
+ my $randbits = $Config{randbits};
+ $max = $min = rand(1);
+ for (1..$reps) {
+ my $n = rand(1);
+ if ($n < 0.0 or $n >= 1.0) {
+ print <<EOM;
+# WHOA THERE! \$Config{drand01} is set to '$Config{drand01}',
+# but that apparently produces values < 0.0 or >= 1.0.
+# Make sure \$Config{drand01} is a valid expression in the
+# C-language, and produces values in the range [0.0,1.0).
+#
+# I give up.
+EOM
+ exit;
+ }
+ $sum += $n;
+ $bits += bits($n * 256); # Don't be greedy; 8 is enough
+ # It's too many if randbits is less than 8!
+ # But that should never be the case... I hope.
+ # Note: If you change this, you must adapt the
+ # formula for absolute standard deviation, below.
+ $max = $n if $n > $max;
+ $min = $n if $n < $min;
+ }
+
+
+ # Hints for TEST 1
+ #
+ # This test checks for one of Perl's most frequent
+ # mis-configurations. Your system's documentation
+ # for rand(2) should tell you what value you need
+ # for randbits. Usually the diagnostic message
+ # has the right value as well. Just fix it and
+ # recompile, and you'll usually be fine. (The main
+ # reason that the diagnostic message might get the
+ # wrong value is that Config.pm is incorrect.)
+ #
+ if ($max <= 0 or $max >= (2 ** $randbits)) {# Just in case...
+ print "# max=[$max] min=[$min]\nnot ok 1\n";
+ print "# This perl was compiled with randbits=$randbits\n";
+ print "# which is _way_ off. Or maybe your system rand is broken,\n";
+ print "# or your C compiler can't multiply, or maybe Martians\n";
+ print "# have taken over your computer. For starters, see about\n";
+ print "# trying a better value for randbits, probably smaller.\n";
+ # If that isn't the problem, we'll have
+ # to put d_martians into Config.pm
+ print "# Skipping remaining tests until randbits is fixed.\n";
+ exit;
+ }
+
+ $off = log($max) / log(2); # log2
+ $off = int($off) + ($off > 0); # Next more positive int
+ if ($off) {
+ $shouldbe = $Config{randbits} + $off;
+ print "# max=[$max] min=[$min]\nnot ok 1\n";
+ print "# This perl was compiled with randbits=$randbits on $^O.\n";
+ print "# Consider using randbits=$shouldbe instead.\n";
+ # And skip the remaining tests; they would be pointless now.
+ print "# Skipping remaining tests until randbits is fixed.\n";
+ exit;
+ } else {
+ print "ok 1\n";
+ }
+
+ # Hints for TEST 2
+ #
+ # This should always be true: 0 <= rand(1) < 1
+ # If this test is failing, something is seriously wrong,
+ # either in perl or your system's rand function.
+ #
+ if ($min < 0 or $max >= 1) { # Slightly redundant...
+ print "not ok 2\n";
+ print "# min too low\n" if $min < 0;
+ print "# max too high\n" if $max >= 1;
+ } else {
+ print "ok 2\n";
+ }
+
+ # Hints for TEST 3
+ #
+ # This is just a crude test. The average number produced
+ # by rand should be about one-half. But once in a while
+ # it will be relatively far away. Note: This test will
+ # occasionally fail on a perfectly good system!
+ # See the hints for test 4 to see why.
+ #
+ $sum /= $reps;
+ if ($sum < 0.4 or $sum > 0.6) {
+ print "not ok 3\n# Average random number is far from 0.5\n";
+ } else {
+ print "ok 3\n";
+ }
+
+ # Hints for TEST 4
+ #
+ # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE
+ # This test will fail .1% of the time on a normal system.
+ # also
+ # This test asks you to see these hints 100% of the time!
+ # NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE
+ #
+ # There is probably no reason to be alarmed that
+ # something is wrong with your rand function. But,
+ # if you're curious or if you can't help being
+ # alarmed, keep reading.
+ #
+ # This is a less-crude test than test 3. But it has
+ # the same basic flaw: Unusually distributed random
+ # values should occasionally appear in every good
+ # random number sequence. (If you flip a fair coin
+ # twenty times every day, you'll see it land all
+ # heads about one time in a million days, on the
+ # average. That might alarm you if you saw it happen
+ # on the first day!)
+ #
+ # So, if this test failed on you once, run it a dozen
+ # times. If it keeps failing, it's likely that your
+ # rand is bogus. If it keeps passing, it's likely
+ # that the one failure was bogus. If it's a mix,
+ # read on to see about how to interpret the tests.
+ #
+ # The number printed in square brackets is the
+ # standard deviation, a statistical measure
+ # of how unusual rand's behavior seemed. It should
+ # fall in these ranges with these *approximate*
+ # probabilities:
+ #
+ # under 1 68.26% of the time
+ # 1-2 27.18% of the time
+ # 2-3 4.30% of the time
+ # over 3 0.26% of the time
+ #
+ # If the numbers you see are not scattered approximately
+ # (not exactly!) like that table, check with your vendor
+ # to find out what's wrong with your rand. Or with this
+ # algorithm. :-)
+ #
+ # Calculating absoulute standard deviation for number of bits set
+ # (eight bits per rep)
+ $dev = abs ($bits - $reps * 4) / sqrt($reps * 2);
+
+ if ($dev < 1.96) {
+ print "ok 4\n"; # 95% of the time.
+ print "# Your rand seems fine. If this test failed\n";
+ print "# previously, you may want to run it again.\n";
+ } elsif ($dev < 2.575) {
+ print "ok 4\n# In here about 4% of the time. Hmmm...\n";
+ print "# This is ok, but suspicious. But it will happen\n";
+ print "# one time out of 25, more or less.\n";
+ print "# You should run this test again to be sure.\n";
+ } elsif ($dev < 3.3) {
+ print "ok 4\n# In this range about 1% of the time.\n";
+ print "# This is very suspicious. It will happen only\n";
+ print "# about one time out of 100, more or less.\n";
+ print "# You should run this test again to be sure.\n";
+ } elsif ($dev < 3.9) {
+ print "not ok 4\n# In this range very rarely.\n";
+ print "# This is VERY suspicious. It will happen only\n";
+ print "# about one time out of 1000, more or less.\n";
+ print "# You should run this test again to be sure.\n";
+ } else {
+ print "not ok 4\n# Seriously whacked.\n";
+ print "# This is VERY VERY suspicious.\n";
+ print "# Your rand seems to be bogus.\n";
+ }
+ print "#\n# If you are having random number troubles,\n";
+ print "# see the hints within the test script for more\n";
+ printf "# information on why this might fail. [ %.3f ]\n", $dev;
}
-if ($c == $n) {print "ok 2\n";} else {print "not ok 2\n"}
+{
+ srand; # These three lines are for test 7
+ my $time = time; # It's just faster to do them here.
+ my $rand = join ", ", rand, rand, rand;
+
+ # Hints for TEST 5
+ #
+ # This test checks that the argument to srand actually
+ # sets the seed for generating random numbers.
+ #
+ srand(3.14159);
+ my $r = rand;
+ srand(3.14159);
+ if (rand != $r) {
+ print "not ok 5\n";
+ print "# srand is not consistent.\n";
+ } else {
+ print "ok 5\n";
+ }
+
+ # Hints for TEST 6
+ #
+ # This test just checks that the previous one didn't
+ # give us false confidence!
+ #
+ if (rand == $r) {
+ print "not ok 6\n";
+ print "# rand is now unchanging!\n";
+ } else {
+ print "ok 6\n";
+ }
+
+ # Hints for TEST 7
+ #
+ # This checks that srand without arguments gives
+ # different sequences each time. Note: You shouldn't
+ # be calling srand more than once unless you know
+ # what you're doing! But if this fails on your
+ # system, run perlbug and let the developers know
+ # what other sources of randomness srand should
+ # tap into.
+ #
+ while ($time == time) { } # Wait for new second, just in case.
+ srand;
+ if ((join ", ", rand, rand, rand) eq $rand) {
+ print "not ok 7\n";
+ print "# srand without args isn't varying.\n";
+ } else {
+ print "ok 7\n";
+ }
+}
+
+# Now, let's see whether rand accepts its argument
+{
+ my($max, $min);
+ $max = $min = rand(100);
+ for (1..$reps) {
+ my $n = rand(100);
+ $max = $n if $n > $max;
+ $min = $n if $n < $min;
+ }
+
+ # Hints for TEST 8
+ #
+ # This test checks to see that rand(100) really falls
+ # within the range 0 - 100, and that the numbers produced
+ # have a reasonably-large range among them.
+ #
+ if ($min < 0 or $max >= 100 or ($max - $min) < 65) {
+ print "not ok 8\n";
+ print "# min too low\n" if $min < 0;
+ print "# max too high\n" if $max >= 100;
+ print "# range too narrow\n" if ($max - $min) < 65;
+ } else {
+ print "ok 8\n";
+ }
+
+ # Hints for TEST 9
+ #
+ # This test checks that rand without an argument
+ # is equivalent to rand(1).
+ #
+ $_ = 12345; # Just for fun.
+ srand 12345;
+ my $r = rand;
+ srand 12345;
+ if (rand(1) == $r) {
+ print "ok 9\n";
+ } else {
+ print "not ok 9\n";
+ print "# rand without arguments isn't rand(1)!\n";
+ }
+
+ # Hints for TEST 10
+ #
+ # This checks that rand without an argument is not
+ # rand($_). (In case somebody got overzealous.)
+ #
+ if ($r >= 1) {
+ print "not ok 10\n";
+ print "# rand without arguments isn't under 1!\n";
+ } else {
+ print "ok 10\n";
+ }
+}
+
+# Hints for TEST 11
+#
+# This test checks whether Perl called srand for you. This should
+# be the case in version 5.004 and later. Note: You must still
+# call srand if your code might ever be run on a pre-5.004 system!
+#
+AUTOSRAND:
+{
+ unless ($Config{d_fork}) {
+ # Skip this test. It's not likely to be system-specific, anyway.
+ print "ok 11\n# Skipping this test on this platform.\n";
+ last;
+ }
+
+ my($pid, $first);
+ for (1..5) {
+ my $PERL = (($^O eq 'VMS') ? "MCR $^X"
+ : ($^O eq 'MSWin32') ? '.\perl'
+ : ($^O eq 'NetWare') ? 'perl'
+ : './perl');
+ $pid = open PERL, qq[$PERL -e "print rand"|];
+ die "Couldn't pipe from perl: $!" unless defined $pid;
+ if (defined $first) {
+ if ($first ne <PERL>) {
+ print "ok 11\n";
+ last AUTOSRAND;
+ }
+ } else {
+ $first = <PERL>;
+ }
+ close PERL or die "perl returned error code $?";
+ }
+ print "not ok 11\n# srand isn't being autocalled.\n";
+}
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