Beefy Boxes and Bandwidth Generously Provided by pair Networks
Pathologically Eclectic Rubbish Lister

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??

One comment that I would make, also, (tangental to the immediate discussion though it be ...) is that unexpectedly-good results can be obtained by using “an old COBOL trick,” namely, use an external disk-sort to sort the file first.   Then, you can simply read the file sequentially.   Every occurrence of every value in every group will be adjacent ... just count ’em up until the value changes (or until end-of-file).   Any gap in the sequence indicates a complete absence of values, anywhere in the original file, that falls into that gap.   The amount of memory required is:   “basically, none.”

And, yes ... you can sort a file of millions of entries and you’ll be quite pleasantly surprised at how well even a run-of-the-mill disk sorter (or Perl module) can get the job done.   It isn’t memory intensive (although it will efficiently use what memory is available).   It is disk-space intensive, as it will create and discard many temporary spill-files, but moderately so.

The same technique is also ideally suited to comparing large files, or for merging them, because there is no “searching” to be done at all.   Merely sort all of the files the same way, and the process is once again sequential.

In reply to Re: "Just use a hash": An overworked mantra? by sundialsvc4
in thread "Just use a hash": An overworked mantra? by davido

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 or How to display code and escape characters are good places to start.
Log In?

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

How do I use this? | Other CB clients
Other Users?
Others lurking in the Monastery: (2)
As of 2021-09-24 18:47 GMT
Find Nodes?
    Voting Booth?

    No recent polls found