I understood your recommendation to not call srandom inside threads. Basically, I'm reporting that PDL::random() results in lesser uniqueness versus CORE::rand(), regardless if calling srandom before spawning threads.

Edit: etj identified a race condition, hence less uniqueness.

use v5.030;
use threads;
use threads::shared;
use PDL;

BEGIN { $PDL::no_clone_skip_warning = 1; }

my $lock : shared = 0;

srandom(3);  # PDL 2.089_01

for my $tid (1..16) {
    threads->create(sub {
        my $output = "";
        for (1..500000) {
          # my $r = CORE::rand();
            my $r = PDL->random;
            $output .= "$r\n";
        }
        lock $lock;
        print $output;
    });
}

$_->join for threads->list;

[download]

CORE::rand()

$ perl test7.pl | wc -l
8000000

$ perl test7.pl | LC_ALL=C sort -u | wc -l
8000000

$ perl test7.pl | LC_ALL=C sort -u | wc -l
8000000

$ perl test7.pl | LC_ALL=C sort -u | wc -l
8000000

[download]

PDL->random

$ perl test7.pl | wc -l
8000000

$ perl test7.pl | LC_ALL=C sort -u | wc -l
7507936

$ perl test7.pl | LC_ALL=C sort -u | wc -l
7446785

$ perl test7.pl | LC_ALL=C sort -u | wc -l
7446785

[download]

In reply to Re^9: PDL and srand puzzle - uniqueness PDL->random vs CORE::rand by marioroy
in thread PDL and srand puzzle by syphilis

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