Hello, Whenever I use undef on a large hash, everything that follows that undef becomes slower. Here is an example: 
########################
#! /usr/local/bin/perl
use strict;
{
    my $i = 0;
    my ;
    my %testHash2;
    my $max = 1000000;
    
    my $startTime = time;
    print "Loading hash 1...\n";
    for($i = 0; $i <= $max; $i++){
        $testHash1{$i} = "THIS IS MY $i PROTEST SONG";
    if($i%100000==0){
             print "Loaded $i\n";
        }
    }
    my $stopTime = time;
    printf("Hash 1 Rows/Sec: %.01f\n",$i/($stopTime-$startTime));
    undef %testHash1;

    $i = 0;
    $startTime = time;
    print "Loading hash 2...\n";
    for($i = 0; $i <= $max; $i++){
        $testHash2{$i} = "THIS IS MY $i PROTEST SONG";
    if($i%100000==0){
             print "Loaded $i\n";
        }
    }
    $stopTime = time;
    printf("Hash 2 Rows/Sec: %.01f\n",$i/($stopTime-$startTime));

}
##############

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On my machine, the inserts to %testHash1 takes place at about 250,000 recs/second. The second insert to %testHash2 inserts at a rate of about 9000 recs/second. If I remove the undef %testHash1. The second batch of inserts is just as fast as the first. I have tried emptying the hash in different ways (%testHash1 = ();...) but the results are always the same. What am I doing wrong? Thanks, Thalej

2005-10-12 Retitled by g0n, as per Monastery guidelines
Original title: 'perl undef'

In reply to Use of undef slowing down perl? by thalej

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