In Perl, how can I wait for threads to end in parallel?
- by Pmarcoen
I have a Perl script that launches 2 threads,one for each processor. I need it to wait for a thread to end, if one thread ends a new one is spawned. It seems that the join method blocks the rest of the program, therefore the second thread can't end until everything the first thread does is done which sort of defeats its purpose.
I tried the is_joinable method but that doesn't seem to do it either.
Here is some of my code :
use threads;
use threads::shared;
@file_list = @ARGV; #Our file list
$nofiles = $#file_list + 1; #Real number of files
$currfile = 1; #Current number of file to process
my %MSG : shared; #shared hash
$thr0 = threads->new(\&process, shift(@file_list));
$currfile++;
$thr1 = threads->new(\&process, shift(@file_list));
$currfile++;
while(1){
if ($thr0->is_joinable()) {
$thr0->join;
#check if there are files left to process
if($currfile <= $nofiles){
$thr0 = threads->new(\&process, shift(@file_list));
$currfile++;
}
}
if ($thr1->is_joinable()) {
$thr1->join;
#check if there are files left to process
if($currfile <= $nofiles){
$thr1 = threads->new(\&process, shift(@file_list));
$currfile++;
}
}
}
sub process{
print "Opening $currfile of $nofiles\n";
#do some stuff
if(some condition){
lock(%MSG);
#write stuff to hash
}
print "Closing $currfile of $nofiles\n";
}
The output of this is :
Opening 1 of 4
Opening 2 of 4
Closing 1 of 4
Opening 3 of 4
Closing 3 of 4
Opening 4 of 4
Closing 2 of 4
Closing 4 of 4
