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Re: Implement uclast with a regex

by dada (Chaplain)
on Mar 10, 2004 at 09:18 UTC ( #335395=note: print w/replies, xml ) Need Help??


in reply to Implement uclast with a regex

yet another way, which should be quickier than the double reverse:
my $string = "ACta"; $string = lc(substr($string, 0, length($string)-1)) . uc(substr($string, -1, 1));
cheers,
Aldo

King of Laziness, Wizard of Impatience, Lord of Hubris

Replies are listed 'Best First'.
Re: mplement uclast with a regex
by Abigail-II (Bishop) on Mar 10, 2004 at 10:12 UTC
    Well, I get it to almost the same speed as the double reverse, but only after some modification:
    #!/usr/bin/perl use strict; use warnings; use Benchmark qw /cmpthese/; chomp (our @strings = <DATA>); our (@a, @b, @c, @d); cmpthese -1 => { juerd => '@a = map {scalar reverse ucfirst lc reverse} @strings', davido => '@b = map {my $t = $_; $t =~ s/^(.*)(.)$/\L$1\U$2/; $t} +@strings', dada1 => '@c = map {lc (substr ($_, 0, length ($string) - 1)) . uc (substr ($_, -1, 1))} @strings', dada2 => '@d = map {lc (substr ($_, 0, -1)) . uc (substr ($_, -1, 1))} @strings', }; die 1 unless "@a" eq "@b"; die 2 unless "@a" eq "@c"; die 3 unless "@a" eq "@d"; __DATA__ ACta abcdefghijklmnopqrstuvwxyz abcdefghijklmnopqrstuvwxyz abcdefghijklmnopqrstuvwxyz abcdefghijklmnop +qrstuvwxyz I have a question! yet another way, which should be quickier than the double reverse: Rate davido dada1 dada2 juerd davido 21081/s -- -68% -70% -70% dada1 65511/s 211% -- -6% -7% dada2 69592/s 230% 6% -- -1% juerd 70275/s 233% 7% 1% --

    Abigail

Re: Re: Implement uclast with a regex
by Juerd (Abbot) on Mar 10, 2004 at 09:43 UTC

    should be quickier than the double reverse

    Why? Have you benchmarked that?

    Juerd # { site => 'juerd.nl', plp_site => 'plp.juerd.nl', do_not_use => 'spamtrap' }

      no I didn't, it was just a guess :-) and in fact, it seems the double reverse solution is faster for small strings, while the substr solution wins in the long run. anyway, here you get full benchmark:
      use strict; use List::Util qw(shuffle); use Benchmark qw(:all); my $string = "ACta"; print "*** ", length($string), " characters\n"; cmpthese(1_000_000, { uclast_substr => sub { uclast_substr($string) }, uclast_2reverse => sub { uclast_2reverse($string) }, }); $string = join ("", shuffle( 'A'..'Z', 'a'..'z' )); print "*** ", length($string), " characters\n"; cmpthese(1_000_000, { uclast_substr => sub { uclast_substr($string) }, uclast_2reverse => sub { uclast_2reverse($string) }, }); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); print "*** ", length($string), " characters\n"; cmpthese(1_000_000, { uclast_substr => sub { uclast_substr($string) }, uclast_2reverse => sub { uclast_2reverse($string) }, }); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); $string .= join ("", shuffle( 'A'..'Z', 'a'..'z' )); print "*** ", length($string), " characters\n"; cmpthese(1_000_000, { uclast_substr => sub { uclast_substr($string) }, uclast_2reverse => sub { uclast_2reverse($string) }, }); sub uclast_substr { my($string) = @_; $string = lc(substr($string, 0, length($string)-1)) . uc(substr($string, -1, 1)); return $string; } sub uclast_2reverse { my($string) = @_; $string = reverse ucfirst lc reverse $string; return $string; }
      and here the result:
      *** 4 characters
                          Rate   uclast_substr uclast_2reverse
      uclast_substr   566572/s              --            -15%
      uclast_2reverse 666223/s             18%              --
      *** 52 characters
                          Rate   uclast_substr uclast_2reverse
      uclast_substr   470588/s              --             -6%
      uclast_2reverse 500000/s              6%              --
      *** 208 characters
                          Rate uclast_2reverse   uclast_substr
      uclast_2reverse 249938/s              --             -9%
      uclast_substr   273523/s              9%              --
      *** 676 characters
                          Rate uclast_2reverse   uclast_substr
      uclast_2reverse 102239/s              --            -19%
      uclast_substr   126231/s             23%              --
      
      cheers,
      Aldo

      King of Laziness, Wizard of Impatience, Lord of Hubris

      use Benchmark; my $tests = [qw(these are a few test to try andaverylongteststring acoupleoftimesover xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx +xxxxxxxxxxxxxxxxxxxxxxxxxx zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz +zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzz)]; timethese (100000, { NoOpLoop => sub { for my $test (@$tests) { # NO Op Loop } }, regex1 => sub { for my $test (@$tests) { $test=~s/^(.*)(.)$/\L$1\U$2/; } }, substr => sub { for my $test (@$tests) { $test= lc(substr($test, 0, length($test)-1)) . uc(substr($test, -1, 1)); } }, reverse=> sub { for my $test (@$tests) { $test=reverse ucfirst lc reverse $test; } } });
      and the winner is :-
      Benchmark: timing 100000 iterations of NoOpLoop, regex1, reverse, subs +tr... NoOpLoop: 2 wallclock secs ( 1.86 usr + 0.00 sys = 1.86 CPU) @ 53763.44/s (n=100000) regex1: 82 wallclock secs (30.31 usr + 0.01 sys = 30.32 CPU) @ 3298.15/s (n=100000) reverse: 8 wallclock secs ( 7.40 usr + 0.00 sys = 7.40 CPU) @ 13513.51/s (n=100000) substr: 8 wallclock secs ( 8.51 usr + 0.01 sys = 8.52 CPU) @ 11737.09/s (n=100000)
      Interesting: double reverse seamed the best but as always test on real data!!

      Hope it helps
      UnderMine

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