Hello all. I am an EE, so while my question may seem to some of you basic, for me it is not. How to efficiently search in a 2 Gig file, w/o risk of running out of memory or two great runtime?

I have the next dillema:
I have 2 text depicting electrical path data. Each one of them can amount to 2Gig. let them be path_p and path_n I have another file, containing paths which were in only one of these files. This file is dif_file Each file may contain two different types, MIN & MAX. i know how to discern one from another These paths are seperated by ^Path (path_number). i.e. each one of these lines means a new path. The file has a header, but not a footer. I need, based on the information in dif_file, find the corresponsing path (using data within it) in the 2Gig file. This better be done with as little runtime as possible from an algorithm point of view, as I don't plan on writing the code in C ;-), and that it would not run out of memory. My initial concpet was this:

1. Get a list for path_n from dif_file
2. get a list for path_n from dif_file
3. Open path_n, read it line by line into a huge hash (reading from ^Path to the next ^Path, and then generating the key, seeing if it fits, keep it, else discard) and then generating the list.
Repeat for path_p
Does anyone have a better concept?

Edit by tye: Preserve formatting

In reply to huge file->hash by ISAI student

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


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.