Re: Null-stripping performance

You'd almost certainly be faster to unpack the entire string into an array once and then just index into the array:

my @numbers = unpack '(a4)*', $string;; ## Requires 5.8.x

sub fetchOne {
    my $index = shift;
    return $numbers[ $index ];
}
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Re^2: Null-stripping performance by qiau (Initiate) on Feb 26, 2007 at 13:52 UTC
Oh, forgot to say that the strings are pretty large so I don't think arrays would be the best solution. Each string is about 1 Mbyte that I read in from a file upon request so a standard use is to open about four files (sometimes more, sometimes less) and read values from different indexes in those strings. I think I tried with a array in the beginning but realized that splitting into 1 Mbyte arrays wasn't fast at all :).	[reply]
Re^3: Null-stripping performance by BrowserUk (Patriarch) on Feb 26, 2007 at 15:45 UTC
You did only do the unpack to an array once--not every time you needed a number--didn't you? If that is the case, I'd benchmark combining substr and unpack against the other options: `my $str = ...; sub fetchOne{ unpack 'a4', substr $str, $_[ 0 ] * 4, 4 }` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l]