On 12/29/2015 12:46 AM, Jules Field (via RT) wrote: > # New Ticket Created by Jules Field > # Please include the string: [perl #127064] > # in the subject line of all future correspondence about this issue. > # <URL: https://rt.perl.org/Ticket/Display.html?id=127064 > > > > Given > my @lines = "some-text.txt".IO.lines; > my $s = 'Jules'; > (some-text.txt is about 43k lines) > > Doing > my @matching = @lines.grep(/ $s /); > is about 50 times slower than > my @matching = @lines.grep(/ Jules /); > > And if $s happened to contain anything other than literals, so I had to us > my @matching = @lines.grep(/ <$s> /); > then it's nearly 150 times slower. > > my @matching = @lines.grep($s); > doesn't appear to work. It matches 0 lines but doesn't die. > > The lack of Perl5's straightforward variable interpolation in regexs is > crippling the speed. > Is there a faster alternative? (other than EVAL to build the regex) >
For now, you can use @lines.grep(*.contains($s)), which will be sufficiently fast. Ideally, our regex optimizer would turn this simple regex into a code that uses .index to find a literal string and construct a match object for that. Or even - if you put a literal "so" in front - turn it into .contains($literal) if it knows that the match object will only be inspected for true/false. Until then, we ought to be able to make interpolation a bit faster. - Timo
