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Postings from November 2009
Nicholas Clark wrote:
> On Wed, Nov 25, 2009 at 10:42:59PM -0700, karl williamson wrote:
>> Oops, forgot to put the function in.
>> karl williamson wrote:
>
>>> So, I tried it with NYTProf. As I expected (I had used DProf earlier),
>>> the highest usage subroutine was my pure Perl version of
>>> Scalar::Util::refaddr, reproduced below. A third of the total time was
>>> spent in this routine. (This is required because miniperl doesn't do
>>> dynamic loading, so refaddr is not available.)
>>>
>>> When I was writing mktables, I was under the impression that refaddr
>>> would be brought into the core for 5.12. There was an agreement to that
>>> effect, but I guess no one ever got around to actually doing it.
>>>
>>> When I run this under perl instead of miniperl, and change objaddr to
>>> just return refaddr, the combination still takes quite a lot of time. If
>>> refaddr were in the core would it be in-lined?
>
>> sub objaddr($) {
>> # Returns the address of the blessed input object. Uses the XS
>> version if
>> # available. It doesn't check for blessedness because that would do a
>> # string eval every call, and the program is structured so that this is
>> # never called for a non-blessed object.
>>
>> return Scalar::Util::refaddr($_[0]) if $has_fast_scalar_util;
>>
>> # Get the package
>> my $pkg = ref($_[0]) or return undef;
>>
>> # Change to a fake package to defeat any overloading
>> bless $_[0], 'main::Fake';
>>
>> # Numifying a ref gives its address.
>> my $addr = 0 + $_[0];
>>
>> # Return to original class
>> bless $_[0], $pkg;
>> return $addr;
>> }
>>
>> I found that any overload in a class caused the numifying to fail if I
>> did it in that class; hence the blesses are necessary.
>
> I have memory of comments being made on IRC about no overloading. Using it
> avoids the need to rebless. With this patch:
>
> diff --git a/lib/unicore/mktables b/lib/unicore/mktables
> index ee51608..b2624f0 100644
> --- a/lib/unicore/mktables
> +++ b/lib/unicore/mktables
> @@ -1133,17 +1133,11 @@ sub objaddr($) {
> return Scalar::Util::refaddr($_[0]) if $has_fast_scalar_util;
>
> # Check at least that is a ref.
> - my $pkg = ref($_[0]) or return undef;
> -
> - # Change to a fake package to defeat any overloaded stringify
> - bless $_[0], 'main::Fake';
> + ref($_[0]) or return undef;
>
> # Numifying a ref gives its address.
> - my $addr = 0 + $_[0];
> -
> - # Return to original class
> - bless $_[0], $pkg;
> - return $addr;
> + no overloading;
> + return 0 + $_[0];
> }
>
> sub max ($$) {
>
> I find that on "my machine" the run time (with ./miniperl) goes down from 47 to
> 38 seconds. That's pretty close to the run time with ./perl (and hence
> real Scalar::Util::refaddr) of 35.5 seconds.
Many thanks
>
> Technically, I think, this falls foul of a strict reading of the feature
> freeze, as it's not a bug fix. Unless "it's too slow" is considered a bug.
>
Ah, but it isn't a new feature; I could argue that mktables isn't even a
new feature, but no point; it met the deadline anyway. I'll submit a
patch with your fix. I'm trying to keep mktables compatible with 5.8 in
case a user wants to apply it; no object recompilations are needed. 'no
overloading' is not a 5.8 feature, so I'll add something to redefine it
when that pragma is not available.
> Nicholas Clark
>
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