Re: •Re: Check whether your hash keys have random order

[liz]

I was trying to save memory by not having to load Config.pm. But because of your remark, I decided to do a Benchmark:

Benchmark: timing 1000 iterations of open, use...
 open: 38 wallclock secs ( 2.62 usr  0.00 sys + 16.14 cusr 12.96 csys = 31.72 CPU) @ 381.68/s (n=1000)
  use: 14 wallclock secs (13.15 usr +  0.00 sys = 13.15 CPU) @ 76.05/s (n=1000)

This surprised me a lot!. The fork() approach with open() seems to be 5 times as fast as loading Config.pm!

Alas, I think I stumbled upon a bug / feature / problem of Benchmark: apparently, only "usr" CPU is taken into account when calculating the number of runs/second, and the "usr" CPU is of course a lot less than with fork/open than it is with use.

Still, the fork/open approach only takes 2.5 times as much CPU as loading Config.pm. I wonder if that is a testament of the efficiency of fork(), or the slowness of Config.pm. ;-)

The code:

use Benchmark;

timethese( 1000, {
 open => sub {
     open my $handle, $^X.' -V:ccflags |';
     my $ccflags = <$handle>;
     delete $INC{'Config.pm'};
 },
 use => sub {
     require Config; Config->import;
     my $ccflags = $Config{ccflags};
     delete $INC{'Config.pm'};
 },
} );

Liz

[Anonymous Monk]

The use version creates a tied perl hash, employing caching ... while the other version doesn't bother to do that and simply matches on a scalar.

perl -d:Trace -V:ccflags
>> Config.pm:1012:     foreach(@_){
>> Config.pm:1013:  config_re($_), next if /\W/;
>> Config.pm:1014:  my $v=(exists $Config{$_}) ? $Config{$_} : 'UNKNOW
+N';
>> Config.pm:988:     exists($_[0]->{$_[1]}) or
>> Config.pm:882:     return $_[0]->{$_[1]} if (exists $_[0]->{$_[1]})
+;
>> Config.pm:885:     my($value, $start, $marker, $quote_type);
>> Config.pm:887:     $quote_type = "'";
>> Config.pm:889:     if ($_[1] eq 'byteorder') {
>> Config.pm:929:   $marker = "$_[1]=";
>> Config.pm:932:   $start = index($config_sh, "\n$marker$quote_type")
+;
>> Config.pm:934:   if ($start == -1) {
>> Config.pm:938:   return undef if ( ($start == -1) &&  # in case it'
+s first
>> Config.pm:940:   if ($start == -1) {
>> Config.pm:947:       $start += length($marker) + 2;
>> Config.pm:949:   $value = substr($config_sh, $start,
>> Config.pm:956:     if ($quote_type eq '"') {
>> Config.pm:963:     $value = undef if $value eq 'undef';
>> Config.pm:964:     $_[0]->{$_[1]} = $value; # cache it
>> Config.pm:965:     return $value;
>> Config.pm:1015:  $v='undef' unless defined $v;
>> Config.pm:1016:  print "$_='$v';\n";
ccflags='-nologo -O1 -MD -DNDEBUG -DWIN32 -D_CONSOLE -DNO_STRICT -DHAV
+E_DES_FCRYPT  -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -D
PERL_MSVCRT_READFIX';
>> Config.pm:1012:     foreach(@_){

Maybe i'm wrong ...