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Postings from November 2009
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.
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.
Nicholas Clark
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