On Sun, 15 Oct 2017 05:19:54 -0700, ddgr...@gmail.com wrote: > 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.
This is Rakudo version 2017.10-143-g0e50993f4 built on MoarVM version 2017.10-58-gad8618468: / $s / took 2.7s and / <$s> / took 7.0s.
