in reply to trim() magic
I tried to see if there were any knobs to twiddle on this one, using dragonchild’s benchmark cases.
First thing I tried: using a recursive call to alias $_. This lets you get rid of the ternary in the for list.
sub trim { return trim( $_ ) if not @_; @_ = @_ if defined wantarray; for ( @_ ) { s/^\s+//, s/\s+$// } return wantarray ? @_ : $_[ 0 ] if defined wantarray; }
On my setup this is about 15% slower for the “inplace replacement of implicit $_” case, but ekes out a few percentage points on the other cases. But it let me proceed to switch from duplicate defined wantarray tests to a duplicate inner loop:
sub trim2 { return trim2( $_ ) if not @_; return map { local $_ = $_; s/^\s+//, s/\s+$//; $_ } @_ if defined wantarray; for ( @_ ) { s/^\s+//, s/\s+$// } }
This gets back most of the lost speed in the “inplace replacement of implicit $_” case, has roughly the same performance in other void contexts, but is also about 50% faster in many other cases, including the IMHO most important one – passing a scalar and assigning to one.
#!/usr/bin/perl use strict; use warnings; use Benchmark qw( cmpthese timethese ); sub trim1 { @_ = $_ if not @_ and defined wantarray; @_ = @_ if defined wantarray; for ( @_ ? @_ : $_ ) { s/^\s+//, s/\s+$// } return wantarray ? @_ : $_[ 0 ] if defined wantarray; } sub trim2 { return trim2( $_ ) if not @_; return map { local $_ = $_; s/^\s+//, s/\s+$//; $_ } @_ if defined wantarray; for ( @_ ) { s/^\s+//, s/\s+$// } } my $cpu = -1; cmpthese timethese $cpu => { undef_default_1 => sub { $_ = ' asdf '; trim1(); }, undef_default_2 => sub { $_ = ' asdf '; trim2(); }, }; cmpthese timethese $cpu => { scalar_default_1 => sub { $_ = ' asdf '; my $n = trim1(); }, scalar_default_2 => sub { $_ = ' asdf '; my $n = trim2(); }, }; cmpthese timethese $cpu => { scalar_passed_1 => sub { my $x = ' asdf '; my $n = trim1( $x ); +}, scalar_passed_2 => sub { my $x = ' asdf '; my $n = trim2( $x ); +}, }; cmpthese timethese $cpu => { list_default_1 => sub { $_ = ' asdf '; my @n = trim1(); }, list_default_2 => sub { $_ = ' asdf '; my @n = trim2(); }, }; cmpthese timethese $cpu => { list_passed_1 => sub { my @l = ( ' asdf ', ' asdf ' ); my @n = + trim1( @l ); }, list_passed_2 => sub { my @l = ( ' asdf ', ' asdf ' ); my @n = + trim2( @l ); }, }; cmpthese timethese $cpu => { undef_passed_1 => sub { my @l = ( ' asdf ', ' asdf ' ); trim1( + @l ); }, undef_passed_2 => sub { my @l = ( ' asdf ', ' asdf ' ); trim2( + @l ); }, };
Sample run:
Benchmark: running undef_default_1, undef_default_2 for at least 1 CPU seconds... undef_default_1: 0 wallclock secs ( 1.05 usr + 0.01 sys = 1.06 CPU) @ 190933.96/s (n=202390) undef_default_2: 1 wallclock secs ( 1.04 usr + 0.00 sys = 1.04 CPU) @ 174121.15/s (n=181086) Rate undef_default_2 undef_default_1 undef_default_2 174121/s -- -9% undef_default_1 190934/s 10% -- Benchmark: running scalar_default_1, scalar_default_2 for at least 1 CPU seconds... scalar_default_1: 1 wallclock secs ( 1.11 usr + 0.00 sys = 1.11 CPU) @ 103321.62/s (n=114687) scalar_default_2: 1 wallclock secs ( 1.11 usr + 0.00 sys = 1.11 CPU) @ 154982.88/s (n=172031) Rate scalar_default_1 scalar_default_2 scalar_default_1 103322/s -- -33% scalar_default_2 154983/s 50% -- Benchmark: running scalar_passed_1, scalar_passed_2 for at least 1 CPU seconds... scalar_passed_1: 1 wallclock secs ( 1.09 usr + 0.00 sys = 1.09 CPU) @ 121405.50/s (n=132332) scalar_passed_2: 2 wallclock secs ( 1.04 usr + 0.00 sys = 1.04 CPU) @ 183794.23/s (n=191146) Rate scalar_passed_1 scalar_passed_2 scalar_passed_1 121406/s -- -34% scalar_passed_2 183794/s 51% -- Benchmark: running list_default_1, list_default_2 for at least 1 CPU seconds... list_default_1: 2 wallclock secs ( 1.09 usr + 0.00 sys = 1.09 CPU) @ 98641.28/s (n=107519) list_default_2: 2 wallclock secs ( 1.04 usr + 0.00 sys = 1.04 CPU) @ 150376.92/s (n=156392) Rate list_default_1 list_default_2 list_default_1 98641/s -- -34% list_default_2 150377/s 52% -- Benchmark: running list_passed_1, list_passed_2 for at least 1 CPU seconds... list_passed_1: 1 wallclock secs ( 1.07 usr + 0.00 sys = 1.07 CPU) @ 80736.45/s (n=86388) list_passed_2: 1 wallclock secs ( 1.08 usr + 0.00 sys = 1.08 CPU) @ 99554.63/s (n=107519) Rate list_passed_1 list_passed_2 list_passed_1 80736/s -- -19% list_passed_2 99555/s 23% -- Benchmark: running undef_passed_1, undef_passed_2 for at least 1 CPU seconds... undef_passed_1: 1 wallclock secs ( 1.07 usr + 0.00 sys = 1.07 CPU) @ 133980.37/s (n=143359) undef_passed_2: 1 wallclock secs ( 1.13 usr + 0.00 sys = 1.13 CPU) @ 138400.00/s (n=156392) Rate undef_passed_1 undef_passed_2 undef_passed_1 133980/s -- -3% undef_passed_2 138400/s 3% --
Makeshifts last the longest.