29/11/2004 01:06:13, Yitzchak Scott-Thoennes <[EMAIL PROTECTED]> wrote:
>On Sun, Nov 28, 2004 at 11:17:40PM +0000, Nigel Sandever wrote:
>> This is the same bug/limitation of threads::shared I reported in perlbug #
30702.
>>
>> Then, it was essentially dismissed as being "working as designed":
>>
>> Nick Ing-Simmons wrote:
>> > When I 1st did the coding for sharing there was a deliberate policy
>> > not to do that. In general the contents of an array or hash can
>> > contain reference loops, so "walking" the contents to share it is
>> > slightly tricky (it has to be done depth first but breaking loops).
>> >
>> > So you are supposed to share the array/hash and then populate it,
>> > and loops etc. are programmer's problem.
>> >
>> > Scalars are shared using raw 'MAGIC' rather than a normal tie, which
>> > is slightly more efficent, and naturally gives access to the
>> > original value.
>>
>> I have to say that I disagree strongly.
>>
>> Whilst writing code to walk an arbitrary array or hash structure is very
>> complex to get right, doing it once, properly, in library code *has* to
>> be better than expecting every user to write their own!
>>
>> Without the ability to share previously populated datastructures, without
>> requiring them to be copied manually, (given that shared datastructures are
>> already duplicated per thread), makes having the notional ability to share
>> anything other than simple scalers almost useless.
>
>I (perhaps erroneously) recall there being the suggestion that an
>additional function be provided to handle populated data structures
>and share() be left unchanged. But no one has come up to bat that I
>know of.
>
I've had a couple of attempts at writing this in Perl--it is awkward--and very,
very slow.
I *think* that the clone() function from the Clone module on CPAN
http://search.cpan.org/src/RDF/Clone-0.15/Clone.xs
could be adapted to do the job. It looks (to my non-XS skilled eyes) to have
all
the requisite logic for handling circular references, magic and other nasties.
I would willingly step up to the bat, but what I know of XS coding you could
write on the back of a postage stamp, and I think that it would require someone
with some serious internals + threads + XS knowledge to hack this. The whole
thing of copying magic is a complete mystery to me.
I just noticed there is a Clone::PP::clone() on CPAN, which from a quick glance
might be adaptable to the task, and I will take a look at that, but I don't see
anything in there that would make it quicker than my previous attempts.
>
>> Add to that, that any attempt to lock() individual elements of a shared data
>> structure fail (upto 5.8.5), and you have a sharing mechnism that is alomost
>> useless.
>
>
>
njs.
