in reply to Re^2: Is it possible to create a single Hash-of-Hash.. with multiple threads..
in thread Is it possible to create a single Hash-of-Hash.. with multiple threads..

Perl Threads implementation so far, seems very inadequate - it is good for primary school student exhibiting how parallel programming works.

That is a wrong conclusion drawn through a lack of understanding.

If you would care to describe your application in detail -- not just generics, but rather scales and reasons; with examples of data and processing requirements -- then you would (probably) get help with finding definitive, practical and efficient solutions to those requirements.

Your OP asks a simplistic question with an obvious answer: Yes, of course a multi-level hash can be constructed using multiple threads. It is simple and trivial:

#! perl -slw
use strict;
use threads;
use threads::shared;

sub displayHash {
    my( $ref, $pad ) = @_;
    return "\n" unless keys %{ $ref };
    my $buf = '';
    for my $key ( sort keys %{ $ref } ) {
        $buf .= "$pad" if length $buf;
        $buf .= "{$key}" . displayHash( $ref->{ $key }, $pad . '   ' )
+;
    }
    return $buf;
}

sub worker {
    my( $ref, $reps ) = @_;

    for( 1 .. $reps ) {
        my $copyRef = $ref;
        for my $step ( map chr( 97 + rand 26 ), 1 .. int( rand 10 ) ) 
+{
            if( exists $copyRef->{ $step } ) {
                $copyRef = $copyRef->{ $step };
            }
            else {
                lock %{ $copyRef };
                $copyRef = $copyRef->{ $step } = &share( {} );
            }
        }
    }
}

our $REPS //= 20;
our $THREADS //= 4;

my %HoHos : shared;

my @threads = map threads->create( \&worker, \%HoHos, $REPS ), 1 .. $T
+HREADS;

$_->join for @threads;

print displayHash( \%HoHos, '' );
__END__
C:\test>junk91 -REPS=7
{b}{l}{w}{g}
{d}{t}{k}{f}{g}{g}{g}{i}{j}
{f}{j}{v}
{g}{s}{g}{h}{g}
{i}{f}{j}{r}{m}{v}{u}{v}{b}
{k}{d}{f}{q}{k}
   {z}{t}{m}{h}{e}{i}
{m}{b}{l}
   {l}{u}{p}{t}{d}{h}
   {q}{k}{y}
{n}{f}{u}{v}{z}{z}{l}
{o}{f}
{p}{u}{s}{w}{n}{t}
{q}{h}
   {y}{k}{d}{l}{a}{n}{a}{i}
{r}{q}{t}{g}
{v}{o}{n}{x}{b}{g}{c}
{w}{a}
{y}{a}
   {d}{y}{j}
{z}{a}{p}{t}{i}{r}{t}
   {y}{i}{g}{c}{v}{z}{z}{k}

[download]

But, it is also probably not very helpful to your real application.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
  • Comment on Re^3: Is it possible to create a single Hash-of-Hash.. with multiple threads..
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Re^4: Is it possible to create a single Hash-of-Hash.. with multiple threads..
by gsat (Initiate) on May 02, 2014 at 16:18 UTC

    Dear Monk BrowserUk! Please take a bow!!

    Thank You so much - for enlightening me :) Indeed - it was my lack of understanding.

    I have found this entire discussion from everybody - very helpful.

    -=-=-=-=-=-=-=-

    Now, I need more :) It seems - me and my code is tired of doing so many .. if exists.. else share.. kinda additives before I do any structure change - and I think no way to avoid that. Now a couple of Questions here:

    Q1. Is there any easier method?

    Q2. Is it possible to grow a local tree or branch data-structure, then create a shared_clone - and graft the new tree to s sub-branch of main shared tree?

    Q3. I have few subroutines to be called many times - based on data - from inside my thread_worker. So far I am lacking depth in understanding or visualizing - how/when multiple threads work on different set of data, while calling a subroutine - does the code-inside-subroutine-block gets a replicated inside the thread uniquely? - else how the sanity is retained? - sorry if I am asking too basic question - maybe it is the case, I am confused - and not clear enough - where is my confusion too..

    Q4. Inside subroutine - do I have to use every variable as local and not-shared?

    Thanks a lot! Again & Again!

[reply]

      1. No.

        You can replace: 

                    if( exists $copyRef->{ $step } ) {
                 $copyRef = $copyRef->{ $step };
             }
             else {
                 lock %{ $copyRef };
                 $copyRef = $copyRef->{ $step } = &share( {} );
             }

        [download]

        With:

                    lock %{ $copyRef };
            $copyRef = $copyRef->{ $step } //= &share( {} )

        [download]

        Which is more compact, but not easier nor more efficient.

      2. Yes.

        Two possibilities:

        1. You can build a normal (non-shared) subhash and when complete, use threads::shared::shared_clone() to make a shared copy of it and assign a reference to the copy to a key/value pair in the main shared hash:
          ...
my %subhash;
... # populate it
lock %mainSharedHash;
$mainSharedHash{ $key } = shared_clone( \%subhash );
...

          [download]
        2. You can create a shared subhash and assign a ref to it without needing to copy:
          ...
my %subhash :shared:
... # populate it
lock %mainSharedHash;
$mainSharedHash{ $key } = \%subhash;

          [download]
      3. I do not understand the question.

        You'll get better answers if you describe your actual application. Ie. Real requirements garner working responses.

      4. Again, your question makes no sense.

        In a subroutine (or anywhere else), you can use unshared variables and/or shared variables as required.

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
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