I'm a bit late in this thread, but I have a similar problem: evaluate the size of a big hash that I have in memory.
I searched perlmonks for some clue on this issue, and I found this thread. I've read your ideas, and I found them very interesting. Anyway I came up with a different approach, and I'd like to share my idea with you so that you can give me feedback.
The idea is quite simple: I build the hash and then use Storable::freeze (see module Storable) to freeze it in memory, and then evaluate the length of it. I had this idea reading the man page of Storable module: here is an example from the man page: 
use Storable qw(store retrieve freeze thaw dclone);

%color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1);

$str = freeze(\%color);
printf "Serialization of %%color is %d bytes long.\n", length($str);

[download]

What do you think of this approach?

marcos

In reply to Re: Re: How to Calculate Memory Needs? by marcos
in thread How to Calculate Memory Needs? by mrbbking

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.