On 2012-07-30 15:47, punit jain wrote:
my $pm = new Parallel::ForkManager(10);
my $count=0;
foreach my $user (@users) {
$pm->start($user) and next;
my $result;
--- do some processing ---
$pm->finish(0, \$result);
}
$pm->wait_all_children;
However the final value of count is not correct. Is there some race
condition on same variable updation by the processes ?
pm -> run_on_finish (
sub {
my $result = @;
if (defined($result)) {
my $count += $result;
}
}
I wonder why you expect a parent variable to be available to a child.
I am ignoring the bugs and style issues in your code, because they are
not relevant to that point.
If you need to merge results from child-processes, it is best to let
those child-processes write to unshared resources. Rows with an
autoincrement-id in a database are often fine for that. A separate file
per child-process on disk can also be fine.
After all children exited, the parent collects all those results and
merges them.
Map: the parent divides the tasks over the children
Reduce: each child reduces its assigned input to a result
Merge: the parent combines all the results into the final result
--
Ruud
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