#! perl -slw
use strict;
use Benchmark qw[ cmpthese ];

our $K ||= 8;
our $N ||= 1000;
our $M ||= 100;
our $CHUNK ||= 80;

our $chunk = ' ' x $CHUNK;
our $BUFFER = ' ' x ( $M * $CHUNK ); 

cmpthese( -10, {
	std => q[
		my %hash;
		for my $key ( 1 .. $N ) {
			$hash{ $key } = '';
			for my $chunk ( 1 .. $M ) {
				$hash{ $key } .= $chunk;
			}
		}
	],
	prealloc => q[
		my %hash;
		for my $key ( 1 .. $N ) {
			$hash{ $key } = ' ' x ( $M * $CHUNK );
			$hash{ $key } = '';
			for my $chunk ( 1 .. $M ) {
				$hash{ $key } .= $chunk;
			}
		}
	],
	gbuf => q[
		my %hash;
		for my $key ( 1 .. $N ) {
			$BUFFER = '';			
			for my $chunk ( 1 .. $M ) {
				$BUFFER .= $chunk;
			}
			$hash{ $key } = $BUFFER;
		}
	],
	lbuf => q[
		my %hash;
		my $buffer = ' ' x ( $M * $CHUNK );
		for my $key ( 1 .. $N ) {
			$buffer = '';			
			for my $chunk ( 1 .. $M ) {
				$buffer .= $chunk;
			}
			$hash{ $key } = $buffer;
		}
	],
	gbuf_keys => q[
		my %hash; keys %hash = $K;
		for my $key ( 1 .. $N ) {
			$BUFFER = '';			
			for my $chunk ( 1 .. $M ) {
				$BUFFER .= $chunk;
			}
			$hash{ $key } = $BUFFER;
		}
	],
	lbuf_keys => q[
		my %hash; keys %hash = $K;
		for my $key ( 1 .. $N ) {
			$buffer = '';			
			for my $chunk ( 1 .. $M ) {
				$buffer .= $chunk;
			}
			$hash{ $key } = $buffer;
		}
	],
});

__END__
P:\test>369770 -N=10000 -K=16384
             Rate       std  prealloc      lbuf      gbuf lbuf_keys gbuf_keys
std       0.858/s        --      -16%      -56%      -56%      -57%      -57%
prealloc   1.03/s       20%        --      -48%      -48%      -48%      -49%
lbuf       1.96/s      128%       91%        --       -0%       -1%       -2%
gbuf       1.96/s      129%       91%        0%        --       -1%       -2%
lbuf_keys  1.98/s      131%       93%        1%        1%        --       -1%
gbuf_keys  2.00/s      133%       95%        2%        2%        1%        --

P:\test>369770 -N=20000 -K=16384
          s/iter       std  prealloc gbuf_keys lbuf_keys      lbuf      gbuf
std         2.36        --      -15%      -50%      -50%      -53%      -53%
prealloc    2.00       18%        --      -41%      -42%      -44%      -45%
gbuf_keys   1.18      100%       70%        --       -1%       -6%       -6%
lbuf_keys   1.17      102%       71%        1%        --       -5%       -6%
lbuf        1.11      112%       80%        6%        5%        --       -1%
gbuf        1.10      114%       81%        7%        6%        1%        --

P:\test>369770 -N=20000 -K=32678
          s/iter       std  prealloc      lbuf      gbuf lbuf_keys gbuf_keys
std         2.36        --      -14%      -53%      -54%      -54%      -54%
prealloc    2.02       17%        --      -45%      -46%      -46%      -46%
lbuf        1.11      111%       81%        --       -2%       -2%       -3%
gbuf        1.10      115%       84%        2%        --       -0%       -1%
lbuf_keys   1.09      116%       85%        2%        0%        --       -1%
gbuf_keys   1.08      118%       86%        3%        1%        1%        --

P:\test>369770 -N=10000 -K=16384 -M=200
             Rate       std  prealloc      lbuf lbuf_keys gbuf_keys      gbuf
std       0.435/s        --      -25%      -60%      -60%      -60%      -61%
prealloc  0.578/s       33%        --      -47%      -47%      -47%      -48%
lbuf       1.09/s      152%       89%        --       -0%       -0%       -1%
lbuf_keys  1.10/s      152%       90%        0%        --       -0%       -1%
gbuf_keys  1.10/s      153%       90%        0%        0%        --       -1%
gbuf       1.11/s      154%       91%        1%        1%        1%        --

P:\test>369770 -N=10000 -K=16384 -M=300
            (warning: too few iterations for a reliable count)

          s/iter       std  prealloc      gbuf lbuf_keys gbuf_keys      lbuf
std         3.61        --      -28%      -63%      -64%      -64%      -64%
prealloc    2.59       40%        --      -49%      -49%      -50%      -50%
gbuf        1.32      173%       96%        --       -1%       -1%       -2%
lbuf_keys   1.31      175%       97%        1%        --       -1%       -2%
gbuf_keys   1.30      177%       98%        1%        1%        --       -1%
lbuf        1.29      179%      100%        2%        2%        1%        --