On Thu, 31 Dec 2015 05:39:24 -0800, ju...@jules.uk wrote: > > > On 29/12/2015 23:05, Timo Paulssen via RT wrote: > > 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 > Many thanks for that. I hadn't thought to use Whatever. > > I would ideally also be doing case-insensitive regexps, but they are > 50 > times slower than case-sensitive ones, even in trivial cases. > Maybe a :adverb for rx// that says "give me static (i.e. Perl5-style) > interpolation in this regex"? > I can see the advantage of passing the variables to the regex engine, > as > then they can change over time. > > But that's not something I want to do very often, far more frequently > I > just need to construct the regex at run-time and have it go as fast as > possible. > > Just thoughts from a big Perl5 user (e.g. MailScanner is 50k lines of > it!). > > Jules
I recently attempted to make interpolating into regexes a little faster. This is what I was using for a benchmark: perl6 -e 'my @l = "sm.sql".IO.lines; my $s = "Perl6"; my $t = now; my @m = @l.grep(/ $s /); say @m.elems; say now - $t' sm.sql is 10k lines, of which 1283 contain the text "Perl6". This is Rakudo version 2017.09 built on MoarVM version 2017.09.1: / $s / took 5.3s and / <$s> / took 16.5s. This is Rakudo version 2017.09-427-gd23a9ba9d built on MoarVM version 2017.09.1-595-g716f2277f: / $s / took 3.2s and / <$s> / took 14.5s. However, if you type the string to interpolate it is *much* faster for literal interpolation. perl6 -e 'my @l = "sm.sql".IO.lines; my Str $s = "Perl6"; my $t = now; my @m = @l.grep(/ $s /); say @m.elems; say now - $t' This takes only 0.33s. This is still nowhere near as fast as grep(*.contains($s)) though, which only takes 0.037s.
