rekey

gistfile1.txt

use Benchmark qw{cmpthese};

sub rekey1(\%\%) {
  my ($key_map, $old_hash) = @_;
return
  map { exists $key_map{$_}
    ? ( $key_map{$_} => $old_hash{$_} )
    : ( $_ => $old_hash{$_} )
  }
  keys %old_hash;
}

sub rekey2(\%\%) {
  my ($key_map, $hash) = @_;
  my %new_hash = %$hash;
  my @good_keys = grep { exists $hash{$_} } keys %$key_map;
  return %new_hash unless @good_keys;
  @new_hash{@{$key_map}{@good_keys}} = delete @new_hash{@good_keys};
  return %new_hash;
}


sub rekey3(\%\%) {
  my ($key_map, $hash) = @_;
  my %new_hash;

  while (my ($k,$v) = each %$hash) {
    $new_hash{ exists $key_map{$k} ? $key_map{$k} : $k } = $v;
  }

  return %new_hash;
}

#sub rekey4(\%\%) {
# my ($key_map, $hash) = @_;
# my %new_hash;
#
# while (my ($k,$v) = each %$hash) {
#   $new_hash{  $key_map{$k} \\ $k } = $v;
# }
#
# return %new_hash;
#}

my %new_keys = map { ( $_ => $_ * 1000 ) } (1 .. 200);
my %hash = map { ($_ => $_ + 3) } (101 .. 300);

cmpthese(10000000, {
  rekey1 => sub { rekey1 %new_keys, %hash },
  rekey2 => sub { rekey1 %new_keys, %hash },
  rekey3 => sub { rekey1 %new_keys, %hash },
# rekey4 => sub { rekey1 %new_keys, %hash },
});