Beefy Boxes and Bandwidth Generously Provided by pair Networks
XP is just a number
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

All true, but in the spirit of DWIMery, this is actually a benign and irrelevant side effect. The creation of PV from a number is something that will automatically re-happen again later. And thus I think hardburn's code was correct. There are no real side effects in that they cannot be recreated later identically and automatically. For example, if the "use threadsafe" was in code that called a Memoize'd function, there may still be no real side effect. And only the caller can tell that, not perl.

my %cache; sub get_from_cache { my $var = shift; unless (exists $cache{$var}) { $cache{$var} = __PACKAGE__->new($var); } $cache{$var}; } my @foos = do { use threadsafe; map { get_from_cache($_)->foo() } @list; };

Assuming that the object does not have non-local side effects (e.g., it reads from a data store, such as a database or the disk, but does not write to it, and the data store is considered locked from writing, or it merely calculates some stuff), such that removing it from the cache and re-creating it will create precisely the same object (especially the same foo()), then there are no technical side effects, and thus would be threadsafe, even if it's not threadsafe from a pure computer-science perspective.

I have exactly this situation in much of my code at work. I would love to see automatic parallelisation of some of what I do - as it is, I'm forced to fork() on unix, and not use threads at all on Windows, just to get consistant, supported speed boosts where I can. Yes, I lose what modifications child processes create in my objects - but since they are all cached and completely reproducable, there is no real side effect from the child code, except for what it writes to disk.

Of course, in order for this to work, we need a way to signify a subset of the code as serial - for example, when writing to a common logfile. Ok, I'll rephrase this: for it to work, I need that serialisation :-)


In reply to Re^2: RFC: Implicit Parallelization Pragma by Tanktalus
in thread RFC: Implicit Parallelization Pragma by hardburn

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others surveying the Monastery: (15)
    As of 2014-11-21 17:45 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      My preferred Perl binaries come from:














      Results (114 votes), past polls