#!perl -w
use strict;
use 5.010;
use Benchmark qw(:all);
use File::Map 'map_file';

my $testfile= "$0.testdata";
my $data= '0123456789' x 20e6;

# Create the test file. This likely means that it is still hot in the cache...
open my $fh, '>', $testfile
    or die "Couldn't create '$testfile': $!";
print {$fh} $data;
undef $fh;

sub tr_in_memory {
    (my $fn)= @_;
    my $count= ($data =~ tr[0][0]);
    $count
};

sub tr_map_file {
    (my $fn)= @_;
    map_file my($content), $testfile;
    my $count= ($content =~ tr[0][0]);
    $count
};

sub tr_via_readline_10_000 {
    my $total_filtered = 0;
    open my $cgs, "<", $testfile;
    local $/ = \10_000; # blocksize
    $total_filtered += tr/0/0/ while <$cgs>;
};

sub tr_via_readline_100_000 {
    my $total_filtered = 0;
    open my $cgs, "<", $testfile;
    local $/ = \100_000; # blocksize
    $total_filtered += tr/0/0/ while <$cgs>;
};

sub tr_via_readline_1_000_000 {
    my $total_filtered = 0;
    open my $cgs, "<", $testfile;
    local $/ = \1_000_000; # blocksize
    $total_filtered += tr/0/0/ while <$cgs>;
};

say sprintf "Running with a dataset of %d", length $data;
cmpthese( 30, {
    'tr_map_file' => \&tr_map_file,
    'tr_in_memory' => \&tr_in_memory,
    'tr_via_readline 10k' => \&tr_via_readline_10_000,
    'tr_via_readline 100k' => \&tr_via_readline_100_000,
    'tr_via_readline 1m' => \&tr_via_readline_1_000_000,
}
);

##</code><code>##

X:\>perl -w tmp.pl
Running with a dataset of 200000000
                       Rate tr_via_readline 10k tr_via_readline 100k tr_via_readline 1m tr_map_file tr_in_memory
tr_via_readline 10k  2.18/s                  --                 -15%               -17%        -71%         -76%
tr_via_readline 100k 2.55/s                 17%                   --                -2%        -66%         -72%
tr_via_readline 1m   2.61/s                 20%                   2%                 --        -66%         -72%
tr_map_file          7.60/s                249%                 198%               191%          --         -18%
tr_in_memory         9.25/s                325%                 263%               254%         22%           --

##</code><code>##

                     s/iter tr_via_readline 10k tr_via_readline 100k tr_via_readline 1m tr_map_file tr_in_memory
tr_via_readline 10k    4.61                  --                 -15%          -17%        -65%         -77%
tr_via_readline 100k   3.91                 18%                   --           -2%        -59%         -72%
tr_via_readline 1m     3.83                 20%                   2%            --        -58%         -72%
tr_map_file            1.60                189%                 145%          140%          --         -32%
tr_in_memory           1.08                327%                 262%          255%         48%           --