Dear Monks,

I tried to randomly select 20 million lines from a 40 million lines file.

I have two questions.

First, how to select the 20 million lines from the file without bias. I have tried to use perl. But it seems perl is not that good for such thing, so I used R to generate 20 million index to create an index file (rand_sorted.txt) and use it to print the selected lines.

Second, my code is as below:

#!/usr/bin/perl -w
use strict;
open RND, "rand_sorted.txt" or die "no file found";
my @rnd;
@rnd = grep {chomp;} <RND>;
close RND;

WILLOP: while (<>){
    chomp;
FORLOP: foreach my $i (@rnd){

   if ($i != $rnd[$#rnd]){ 
    if ($. == $i){
        print "$_\n";
        shift @rnd;
        last FORLOP;
        }
          else {
            print "$_\n";
            last FORLOP;
        }      
    }

[download]

This works fine and fast for me, but I just hate these two loops nested each other, it looks stupid, or maybe it's stupid. Any one can give me an idea how to do it? Thanks.

In reply to A series of random number and others by lightoverhead

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