If one writes java code in Perl one should not be surprised of the bad performance.

The following is a more perlish version:

use Modern::Perl;
use Time::HiRes qw/time/;

my $start = time;
my $top   = 550;
my $max   = 100;
my @primes;
my $prime;

for ( 2 .. $top ) {
    $prime = $_;
    next if $primes[$_];
    last unless --$max;
    {
        local $_;
        $primes[ $_ * $prime ] = 1 for 2 .. $top / $prime;
    }
}
my $found = time;
say $_ for ( grep { !$primes[$_] } 2 .. $prime );

my $end = time;
say sprintf "Found all:    %.6f seconds", ( $found - $start );
say sprintf "Printing all: %.6f seconds", ( $end - $found );
say sprintf "Running time: %.6f seconds", ( $end - $start );

[download]
Output:
2
3
5
7
11
13
17
19
23
29
31
...
491
499
503
509
521
523
541
Found all:    0.000692 seconds
Printing all: 0.000879 seconds
Running time: 0.001571 seconds

[download]
This application of the Sieve of Erasthotenes finds 100_000 primes in 3 seconds (and then takes 6 seconds to print them on the screen), so it is pretty fast.

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

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

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