在 Perl 中，如何等待线程并行结束？

我有一个 Perl 脚本，它启动 2 个线程，每个处理器一个。我需要它等待线程结束，如果一个线程结束，就会生成一个新线程。看来 join 方法会阻塞程序的其余部分，因此第二个线程无法结束，直到第一个线程所做的所有事情都完成为止，这违背了它的目的。

我尝试过is_joinable方法，但这似乎也不起作用。

这是我的一些代码：

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";
}

其输出是：

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

首先，对代码本身进行一些评论。您需要确保您拥有：

use strict;
use warnings;

在。。。之初every脚本。第二：

@file_list = @ARGV;      #Our file list
$nofiles = $#file_list + 1; #Real number of files 

是不必要的，因为标量上下文中的数组计算为数组中的元素数量。那是：

$nofiles = @ARGV;

会正确地给你文件的数量@ARGV无论其价值如何$[.

最后，通过在启动线程之前对文件列表进行分区，可以使脚本变得更加简单：

use strict; use warnings;

use threads;
use threads::shared;

my @threads = (
    threads->new(\&process, @ARGV[0 .. @ARGV/2]),
    threads->new(\&process, @ARGV[@ARGV/2 + 1 .. @ARGV - 1]),
);

$_->join for @threads;

sub process {
    my @files = @_;
    warn "called with @files\n";
    for my $file ( @files ) {
        warn "opening '$file'\n";
        sleep rand 3;
        warn "closing '$file'\n";
    }
}

Output:

C:\Temp> thr 1 2 3 4 5
called with 1 2 3
opening '1'
called with 4 5
opening '4'
closing '4'
opening '5'
closing '1'
opening '2'
closing '5'
closing '2'
opening '3'
closing '3'  

或者，您可以让线程在完成后继续执行下一个任务：

use strict; use warnings;

use threads;
use threads::shared;

my $current :shared;
$current = 0;

my @threads = map { threads->new(\&process, $_) } 1 .. 2;
$_->join for @threads;

sub process {
    my ($thr) = @_;
    warn "thread $thr stared\n";

    while ( 1 ) {
        my $file;
        {
            lock $current;
            return unless $current < @ARGV;
            $file = $ARGV[$current];
            ++ $current;
        }
        warn "$thr: opening '$file'\n";
        sleep rand 5;
        warn "$thr: closing '$file'\n";
    }
}

Output:

C:\Temp> thr 1 2 3 4 5
thread 1 stared
1: opening '1'
1: closing '1'
1: opening '2'
thread 2 stared
2: opening '3'
2: closing '3'
2: opening '4'
1: closing '2'
1: opening '5'
1: closing '5'
2: closing '4'