Re: Performance Tuning: Searching Long-Sequence Permutations

$permutations_total++ while $string =~ $promoters_regex[$j];
[download]

I guess you want:

$permutations_total++ while $string =~ /$promoters_regex[$j]/g;
[download]

here, otherwise you'll never terminate once there's a match. But now, qr will actually be slower, because you're are interpolating the compiled regex, and recompiling it. And if there are many matches, some gain could be made by writing it as:

{  no warnings 'numeric';
   $permutations_total += $string =~ /$promoters_regex[$j]/g;
}
[download]

Abigail

Comment on Re: Performance Tuning: Searching Long-Sequence Permutations Select or Download Code

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Re: Re: Performance Tuning: Searching Long-Sequence Permutations by chip (Curate) on Jun 27, 2003 at 02:40 UTC
WRT interpolation in /$pat/g: Actually it is fast. When the entire pattern consists of an interpolated qr reference, no recompilation takes place at runtime, so the speed gain of precompilation is not lost. You can observe this with a combination of `perl -Dts` and reading the source code of `pp_regcomp`. WRT the missing //g: It's a fair cop, but society's to blame. :-) -- Chip Salzenberg, Free-Floating Agent of Chaos	[reply] [d/l] [select]
Re: Re: Performance Tuning: Searching Long-Sequence Permutations by diotalevi (Canon) on Jun 27, 2003 at 04:09 UTC
As I stated in /o is dead, long live qr//!, the form `/$promoters_regex[$j]/g` is not interpolated. The qr object is the entire regex and is not stringified. Your expected overhead does not materialize in this case. Writing it as `/ $promoters_regex[$j] /gx` would trigger the recompilation overhead though.	[reply] [d/l] [select]
Re: Re: Performance Tuning: Searching Long-Sequence Permutations by Jasper (Chaplain) on Jun 27, 2003 at 13:17 UTC
Never thought I'd be correcting Abigail, but this will only add 1 to $permutations total. A //g match in scalar context only ever returns 1 (or 0), no matter how many times it matches. Unfortunately, to make it work, you have to run it through an array first `$permutations_total += @array = $string =~ /$promoters_regex[$j]/g;` [download] Which isn't very nice. Don't know how to get around that. Jasper	[reply] [d/l]
Re: Performance Tuning: Searching Long-Sequence Permutations by Abigail-II (Bishop) on Jun 27, 2003 at 13:23 UTC
Eh, right, but it doesn't have to be an array. A list will do, even if it's empty: `$permutations_total += () = $string =~ /$promoters_regex[$j]/g;` [download] Abigail	[reply] [d/l]
Re: Re: Re: Performance Tuning: Searching Long-Sequence Permutations by diotalevi (Canon) on Jun 27, 2003 at 13:25 UTC
Assign it to an empty list. `$permutations_total += () = $string =~ /$promoters_regex[$j]/g`.	[reply] [d/l]