"But the biggest lesson...the obvious optimisation..."

"Du sprichst ein großes Wort gelassen aus." (Johann Wolfgang von Goethe)

Very impressive and instructional. What else should i say?

Update:

There are two little things i would like to add:

My basic theme wasn't to calculate factorials using threads.

I wanted to explore multithreading and thought the best idea would be to use some "expensive" calculation for this. Like in a classic homework.

Unfortunately you provided a much better algorithm that avoids multithreading ;-)

I fear i hit a basic problem in this context.

And apropos little quirks:

I wrote:

sub process {
    my $number = shift;
    # lock %result;
    $result{ threads->tid() } =
      shared_clone( { $number => factorial($number) } );
    $semaphore->up;
}
[download]

It seems like i really need to say something like:

for my $key ( sort { $a <=> $b } keys %result ) {
    my $ref = $result{$key};
    while ( my ( $k, $v ) = each %{$ref} ) {
        say qq($k => $v);
    }
}
[download]

...to iterate over the results. From the docs:

"each HASH does not work properly on shared references embedded in shared structures"

Thanks for this advice and my best regards, Karl

I'm struggling with this:

$Q->enqueue( 1000..2000, (undef) x 4 );
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The docs say:

->enqueue(LIST)
Adds a list of items onto the end of the queue.
[download]

I dumped it:

karls-mac-mini:monks karl$ ./queue.pl 
bless({
  # tied threads::shared::tie
  queue => [
    # tied threads::shared::tie
    1000 .. 2000,
    undef,
    undef,
    undef,
    undef,
  ],
}, "Thread::Queue")
Took 13.820966 seconds
[download]

What are the four undefs good for?

Best regards, Karl

P.S.: But my box is faster than yours ;-)

What are the four undefs good for?

They cause these loops to terminate:

while( my $number = $Q->dequeue ) {
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P.S.: But my box is faster than yours ;-)

No surprise there. My Q6600 is over 7 years old.

Mind you, I make better use of it than most people do of their Haswells :)

---

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". I'm with torvalds on this

In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked

"Mind you, I make better use of it than most people do of their Haswells"

Indeed.

"They cause these loops to terminate"

I guess it works like this:

| 1000  1001  1002  1003 |
| 4 threads ------------ |

| 1004  1005  1006  1007 |
| 4 threads ------------ |

... until they meet undef

| undef undef undef undef|
| 4 threads ------------ |
[download]

Best regards, Karl (still locked/blocked)

«The Crux of the Biscuit is the Apostrophe»