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Re: Why is the size even bigger after pack?

by grantm (Parson)
on Nov 03, 2011 at 04:37 UTC ( #935581=note: print w/ replies, xml ) Need Help??


in reply to Why is the size even bigger after pack?

Devel::Size it telling you how many bytes are taken up by the C structure(s) that are used to represent your Perl variable. The numbers you're getting suggest it takes 24 bytes to represent a scalar containing an integer and 48 bytes to represent a scalar containing a string. I can't say I find that particularly surprising.


Comment on Re: Why is the size even bigger after pack?
Re^2: Why is the size even bigger after pack?
by PerlOnTheWay (Scribe) on Nov 03, 2011 at 05:23 UTC

    What's the point of pack if it takes more memory after packing?

      What did you think it would do?

      pack turns a list of values into a string according to a specific format. If you want to interact with something else which expects values in a specific format (a system call, a foreign function, a binary protocol), pack is your tool. If you want to use less memory, you need something else.


      Improve your skills with Modern Perl: the free book.

      Your example only shows one single case. An SV can hold IV's as well as PV's at the same time and a PV representation of 1 takes less space than that of big numbers. YMMV (even with different versions of perl):

      $ cat test.pl use v5.12; use Devel::Size "total_size"; for my $num (1, 1000, 100_000_000) { say "Value $num:"; say total_size ($num); say total_size (pack "w*", $num); } for my $num ("1", "1000", "100_000_000") { say "Value $num:"; say total_size ($num); say total_size (pack "w*", $num); } $ perl test.pl Value 1: 64 48 Value 1000: 64 48 Value 100000000: 72 48 Value 1: 48 48 Value 1000: 48 48 Value 100_000_000: 56 48 $

      Enjoy, Have FUN! H.Merijn

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