This section provides a tutorial example to test performance of 2 Perl built-in functions: substr() and index() on a Window 2000 system.
I wrote the following program, SubstringTest.pl, in 2002 on a Windows 2000 system to check
the performance of Perl built-in functions: substr() and index():
#- SubstringTest.pl
#- Copyright (c) 2002 by Dr. Herong Yang, http://www.herongyang.com/
#
($numChar, $numTest) = @ARGV;
$numChar = 10 unless $numChar;
$numTest = 1 unless $numTest;
$baseString = &setString($numChar);
$subString = &setString($numChar);
$startTime = time();
$numMatch = 0;
for ($i=0; $i<$numTest; $i++) {
$numMatch = &test();
}
$endTime = time();
$totalTime = $startTime - $endTime;
$averageTime = $totalTime/$numTest;
print("Number of tests = $numTest\n");
print("Number of characters = $numChar\n");
print("Number of matches = $numMatch\n");
print("Total time = $totalTime seconds\n");
print("Average time = $averageTime seconds\n");
exit;
sub setString {
local($size) = @_;
local $str = "";
local($i,$n,$c);
for ($i=0; $i<$size; $i++) {
$n = int(rand(96)) + 32;
$c = chr($n);
$str .= $c;
}
return $str;
}
sub test {
local($i,$j,$l);
local $str = "";
local $num = 0;
local $pos = -1;
for ($i=0; $i<$numChar; $i++) {
$l = $i+1;
for ($j=0; $j<$numChar-$i; $j++) {
$str = substr($subString,$j,$l);
$pos = index($baseString,$str);
$num++ if ($pos<0);
}
}
return $num;
}
The idea is to get two strings of the same length randomly, take all possible substrings
out of the first one, and try to match them in the other one with index().
Running this program with ActivPerl v5.6.1 on Windows 2000 system gave me:
>SubstringTest.pl 50 1000
Number of tests = 1000
Number of characters = 50
Number of matches = 1257
Total time = 8 seconds
Average time = 0.008 seconds
>SubstringTest.pl 100 1000
Number of tests = 1000
Number of characters = 100
Number of matches = 4976
Total time = 31 seconds
Average time = 0.031 seconds
>SubstringTest.pl 200 1000
Number of tests = 1000
Number of characters = 200
Number of matches = 19916
Total time = 137 seconds
Average time = 0.137 seconds
