Beefy Boxes and Bandwidth Generously Provided by pair Networks
Just another Perl shrine
 
PerlMonks  

comment on

( [id://3333]=superdoc: print w/replies, xml ) Need Help??
If the file is not so big that the keys will not fit into memory you can do this:
#!/usr/bin/perl use strict; use warnings; use vars qw( @data $prev $IN @sorted $OUT); $prev = 0; open($IN, '<', 'data'); while (<$IN>) { chomp; my $next = tell($IN); my ($key) = /^([^\s]*)/; push(@data, [ $key, $prev, $next - $prev ]); $prev = $next; } close($IN); @sorted = sort( { $a->[0] cmp $b->[0] } @data); open($IN, '<', 'data'); open($OUT, '>', 'sorteddata'); for (@sorted) { seek($IN, $_->[1], 0); sysread($IN, my $line, $_->[2]); print $OUT $line; } close($IN); close($OUT);
On the cooked data I tested, I got the following timings:
Gnu Sort:
# time sort --temporary-directory=/opt data > sort1

real    0m24.698s
user    0m22.539s
sys     0m1.950s

Perl Sort:
# time perl sort.pl 

real    0m55.900s
user    0m39.897s
sys     0m6.430s
The data file I used had a wc of:
#wc data
  4915200  34406400 383385600 data
I am surprised that this Perl script is only half the speed of Gnu sort on this data. I think that on a bigger data set, with long lines, it might even be able to sort faster that Gnu Sort.

UPDATE: Most of the time seems to be being spent in the output loop. All of the seeks seems to really slow things down.

-- gam3
A picture is worth a thousand words, but takes 200K.

In reply to Re: sorting very large text files by gam3
in thread sorting very large text files by rnaeye

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others taking refuge in the Monastery: (4)
As of 2024-03-29 13:25 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found