I noticed that the comparison is not the same between the two versions.

  • Java version:   if ($composite == 1)
  • Perl version:   if (! $composite)

    • The Perl version is finding primes where the Java version is just printing the first 100 numbers that come along. That is why it was so fast.

    #!/usr/bin/perl
use warnings;
use strict;

my $maxprimes=100;  
my $value=1;  
my $count=0;  
my $start=time();  
print "Printing the first $maxprimes numbers that are prime... \n";  
while ($count < $maxprimes)   
{  
   $value++;  
   my $composite=0;#false  
   OUTER:   
      for (my $i=2; $i < $value; $i++)   
      {  
         INNER:  
            for (my $j=$i; $j<$value; $j++)   
            {  
               if (($j*$i) == $value)   
               {  
                  $composite=1;#true  
                  last OUTER;  
               }  
            }  
      }  
#      if (! $composite)   #this works
      if ($composite == 1)  #from the java section, doesn't work
      {  
         $count++;  
         print "$value is prime\n";  
      }  
}  
my $time = (time() - $start);  
print "Took $time seconds.";

    [download]

    Update: It looks like it prints the non-prime numbers.

    Printing the first 100 numbers that are prime... 
4 is prime
6 is prime
8 is prime
9 is prime
10 is prime
12 is prime
14 is prime
15 is prime
.
.
.
128 is prime
129 is prime
130 is prime
132 is prime
133 is prime
Took 0 seconds.

    [download]

    In reply to Re: performance of perl vs java by Lotus1
    in thread performance of perl vs java by Anonymous Monk

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