Re: XML::Twig and threads

[remiah]

Hello, grizzley.

I have little experience for huge XML files, so I take ready made 100MB xml sample file for example.

Does your colleague have free memory while his process? XML::Twig will eat up memory for large XML files without "purge" or "flush".

Bellow is my test script, counting text tag in two ways.

use strict; use warnings; use XML::Twig;
use Time::HiRes;

my $cnt1=0;
my $b1=Time::HiRes::time();
XML::Twig->new(
    twig_roots => {
        'text' => sub{ $cnt1++; $_[0]->purge;}, 
    },
)->parsefile("standard");
my $e1=Time::HiRes::time();

my $cnt2=0;
my $b2=Time::HiRes::time();
XML::Twig->new(
    twig_roots =>{
        '/site/regions/africa//text' => sub{$cnt2++;},
    },
)->parsefile("standard");
my $e2=Time::HiRes::time();

print "1. text count=$cnt1, time=".($e1-$b1)."\n";
print "2. text count=$cnt2, time=".($e2-$b2)."\n";



__DATA__
1. text count=105114, time=111.188741922379
2. text count=1657, time=60.9104990959167

When I forget to purge(), first example eated up my memory and coredumped. Sometimes, purge() needs some care because it purges inner most element (XML Newbie 's example of Twig has some relation to it).

And if you can squeeze the range with xpath like expression, it could become faster.

I agree with other monks opinions ...
regards.

[grizzley]

He does 'flush' and there are some xpath expressions. I've attached script and fake example XML to original node. It doesn't look like bad design and yet I hope something can be improved there.

[remiah]

I understand your situation at last.
So, copying original and reuse it will be like this.

my $t= XML::Twig->new();
$t->parsefile($inputFile);
my $someData =$t->root->first_child; #someData

for my $i(1 .. $loop) {
    for ( $someData->children_copy( 'managedObject') ){
        handle_managedObject($t, $_);
    }

    print "Iteracja: $i / $loop \t->  OK\n";
    $bID++;
    $someID = 0;
}

It becomes slower than original with my machine. Because deep coping Elt object takes too much time for large XML. I wonder is this same at your environment? Or maybe you already know this ...

As BrowserUK says, use strict and warning please.

[BrowserUk]

I think the real problem is even worse in that with the real, 10MB & 100MB XML files, he is moving his process into swapping hence everything slows to a crawl.