Re: Does Perl do constant anonymous hash creation optimisation?

Even if Perl did detect the constant nature of the inline hashes, which I seriously doubt it could, something like this is probably clearer

use constant {
    SUBSTITUTES =>       { # substitute these
        'DUTCH'       => 'NETHERLANDS',
        'GERMANY'     => 'DEUTSCHLAND',
        'AUST.'       => 'AUSTRALIA',
    },
    SKIPWORDS => { # skip these
        'BANK'        => 1,
        'CORP'        => 1,
        'GOVERNMENT'  => 1,
        'GOVT'        => 1,
        'LIMITED'     => 1,
        'LTD'         => 1,
        'NPV'         => 1,
        'COM'         => 1,
   },
};
    
sub words {
  return [
    map { 
        SUBSTITUTES->{$_} or $_ 
    } grep { 
        !SKIPWORDS->{$_}
    } split /\s+/, shift ];
}
[download]

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

Comment on Re: Does Perl do constant anonymous hash creation optimisation? Download Code

Replies are listed 'Best First'.
Re^2: Does Perl do constant anonymous hash creation optimisation? by jaa (Friar) on Jul 08, 2006 at 14:21 UTC
Thanks for that - have never really used `use constant {...};` [download] we usually do this at the top of the package `our $SKIPWORDS = {};` [download] so I wonder if there is an overhead for use constant? The thing I like about the inline/anon hashes is that all the logic and data is clearly seen in one place. In this specific example, the package is 5000+ lines long, and the words() function because it starts with w... will end up near the end of the file - 5000 lines away from the skip and substitute words. Will probably go with the use contant if there is no overhead - this func will get called a lot in an inner loop with anywhere up to a million times per run. Thanks again, for the pointers, Jeff	[reply] [d/l] [select]
Re^3: Does Perl do constant anonymous hash creation optimisation? by BrowserUk (Patriarch) on Jul 08, 2006 at 15:53 UTC
Using constant is 3 times faster than your inline construct. Read more... (3 kB) In this specific example, the package is 5000+ lines long, and the words() function because it starts with w... will end up near the end of the file - 5000 lines away from the skip and substitute words. With that much data, I'd definitely be putting it in a separate file on it's own. If you do not want to go to the bother of wrapping it up as a module, you could just put the constant hash definition into a file of it's own and use the simple `do 'wordshash.pl';` just before the associated `words()` functions, though it would probably be better to wrap the function and data into a module and do something like `use My::Words qw[ words ];` in the main code. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal? "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re^4: Does Perl do constant anonymous hash creation optimisation? by jaa (Friar) on Jul 08, 2006 at 17:34 UTC
Fab! Thanks very much! I am going to keep this to remind me how to performance test my funcs better in the future. Regards, Jeff	[reply]
Re^3: Does Perl do constant anonymous hash creation optimisation? by jaa (Friar) on Jul 10, 2006 at 15:06 UTC
Dear Monks, Extending the cmpthese() example, I found no appreciable performance difference between: `use constant SKIPWORDS => {...}; our $SKIPWORDS = {};` [download] So a big thumbs up for use constant()! Thanks for the help! Jeff	[reply] [d/l]