12 # If we don't say anything, maybe nobody will notice.
13 # print STDERR "\nWarning: I'm testing the speedup. This might take up to thirty seconds.\n ";
18 # This next test finds an example that takes a long time to run, then
19 # checks to make sure that the run is actually speeded up by memoization.
20 # In some sense, this is the most essential correctness test in the package.
22 # We do this by running the fib() function with successfily larger
23 # arguments until we find one that tales at leasrtt $LONG_RUN seconds
24 # to execute. Then we memoize fib() and run the same call cagain. If
25 # it doesn't produce the same test in less than one-tenth the time,
26 # something is seriously wrong.
28 # $LONG_RUN is the number of seconds that the function call must last
29 # in order for the call to be considered sufficiently long.
36 fib($n-1) + fib($n-2);
39 sub max { $_[0] > $_[1] ?
53 $ELAPSED = time - $start;
54 last if $ELAPSED >= $LONG_RUN;
56 print "# fib($N) took $ELAPSED seconds.\n" if $N % 1 == 0;
57 # we'd expect that fib(n+1) takes about 1.618 times as long as fib(n)
58 # so now that we have a longish run, let's estimate the value of $N
59 # that will get us a sufficiently long run.
60 $N += 1 + int(log($LONG_RUN/$ELAPSED)/log(1.618));
61 print "# OK, N=$N ought to do it.\n";
62 # It's important not to overshoot here because the running time
63 # is exponential in $N. If we increase $N too aggressively,
64 # the user will be forced to wait a very long time.
70 print "# OK, fib($N) was slow enough; it took $ELAPSED seconds.\n";
71 print "# Total calls: $COUNT.\n";
78 $ELAPSED2 = time - $start + .001; # prevent division by 0 errors
80 print (($RESULT == $RESULT2) ? "ok 1\n" : "not ok 1\n");
81 # If it's not ten times as fast, something is seriously wrong.
82 print (($ELAPSED/$ELAPSED2 > 10) ? "ok 2\n" : "not ok 2\n");
83 # If it called the function more than $N times, it wasn't memoized properly
84 print (($COUNT > $N) ? "ok 3\n" : "not ok 3\n");
86 # Do it again. Should be even faster this time.
90 $ELAPSED2 = time - $start + .001; # prevent division by 0 errors
92 print (($RESULT == $RESULT2) ? "ok 4\n" : "not ok 4\n");
93 print (($ELAPSED/$ELAPSED2 > 10) ? "ok 5\n" : "not ok 5\n");
94 # This time it shouldn't have called the function at all.
95 print ($COUNT == 0 ? "ok 6\n" : "not ok 6\n");