Hi monks, I have a list of 121,000 fasta headers in a .txt file and I want to compare this to a multiple FASTA file containing 132,000 sequences. I have written a script to do this but it is too slow!!! The script puts all the lines from the .txt file in a hash and then compares the header of each FASTA sequence in the multiple FASTA file with the keys in the hash and if they match prints out a new FASTA sequence with the renamed header from the .txt file. Is there anything sensible I can do to speed this up?

Input txt file looks like:

F0Z7V0F01A03EB_210
F0Z7V0F01A03EB_180
F0Z7V0F01A03EB_136
F0Z7V0F01A03EB_362
F0Z7V0F01A03GP_298
F0Z7V0F01A03GP_205
etc...........
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Input FASTA looks like:

>GJKKTUG01DYDGC
GGGTATTCCTTCTCCACCTTGCAGCTAACATCAGTGTTTCGTCTACTCAAGCACGCCAAC
ACGCCCTAGAGCGCCCTGTCCAGGGGATGGCAACCAACTCTGACCCTGCAAGTGCAGCAG
ACATGAGGAATACAAACTACAATCTTTTACTTGATGATGCAATGCCGGACAAACTCTAGA
>F0Z7V0F01EDB3V
AAGGCGAGNGGTATCACGCAGTAAGTTACGGTTTTCGGGTAACGCGTCNGNGGNACTAAC
CCACGGNGGGTAACCCGTCNCTACCGGTATAGGACTAAGGTTACCGGAACGTCGTGGGGT
ACCCCCCGGACGGGGACCGTCCCCTCATANAGTCAACNGTNTGAGATGGACTAACTCAAA
CCTAGTTTCAAGTACTATTTAACTTACTTACGTTACCCGTAATTTCGGCGTTTAGAGGCG

etc....................
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My script which is working VERY slowly is :

#!/usr/bin/perl

use strict;
use warnings;
use Bio::SeqIO;
use Data::Dumper;
my %seq_id;
my $fasta_id;
        open HEADER , "<FASTA.headers" or die $!;
        while (<HEADER>){
            chomp $_;
            #print $_."\n";
            $fasta_id = $_; 
            $fasta_id =~ s/_.*//g ;
            #print $fasta_id."\n";                
            %seq_id = ("$fasta_id" => "$_");
#            print Dumper (\%seq_id);


            my $infile=$ARGV[0] || die ("Please give me an input fasta
+ file\n");
            my $inseq = new Bio::SeqIO(-format => 'fasta',
                        -file => $infile);
            while (my $seq_obj = $inseq->next_seq ) {
             my $id = $seq_obj->id ;
            chomp $id;
#            print $id."\n";
            my $seq = $seq_obj->seq ;
                if (exists ($seq_id{$id})) {
                print ">";
                print $seq_id{$fasta_id};
                print "\n".$seq."\n";
                } 
                

            }
}
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