in reply to Re: Why is "for" much slower than "while"?
in thread Why is "for" much slower than "while"?
I don't think this is the complete answer as
is faster than the for.read $IN1, my $buffer, -s $IN1; ++$counts{$_} for split( /^/m, $buffer );
/dev/null Rate for read while for 362612/s -- -7% -19% read 389496/s 7% -- -13% while 449755/s 24% 15% -- /usr/share/dict/words Rate for read while for 4.73/s -- -17% -37% read 5.73/s 21% -- -24% while 7.55/s 60% 32% -- /etc/passwd Rate for while read for 14434/s -- -17% -21% while 17297/s 20% -- -6% read 18355/s 27% 6% --
#!/usr/bin/perl use strict; use Benchmark qw( cmpthese ); foreach my $file qw ( /dev/null /usr/share/dict/words /etc/passwd ) { open my $IN1, '<', $file or die "could not open $file"; my @list = <$IN1>; seek( $IN1, 0, 0 ); print "$file\n"; cmpthese( -5, { for => sub { seek( $IN1, 0, 0 ); my %counts = (); ++$counts{$_} for <$IN1>; die unless keys %counts == @list; }, while => sub { seek( $IN1, 0, 0 ); my %counts = (); ++$counts{$_} while <$IN1>; die unless keys %counts == @list; }, read => sub { seek( $IN1, 0, 0 ); my %counts = (); read $IN1, my $buffer, -s $IN1; ++$counts{$_} for split( /^/m, $buffer ); die unless keys %counts == @list; }, } ); }
-- gam3
A picture is worth a thousand words, but takes 200K.
A picture is worth a thousand words, but takes 200K.
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