Question

我有一个运行速度很慢的功能。我需要在程序的主要部分输入该函数。所以我想做一些类似于UNIX命令yes的东西，它产生尽可能多的输入，但只需要多一点。与yes不同，我不想要STDIN中的值，但我想要Perl队列中的值。

换句话说：这个问题不是关于文件句柄的选择，而是关于线程维护的队列。

我认为元代码看起来与此类似：

my $DataQueue = Thread::Queue->new();

my @producers;
my $no_of_threads = 10;
for (1..$no_of_threads) {
  push @producers, threads->create(\&producer);
}

for(<>) {
  # This should block until there is a value to dequeue
  # Maybe dequeue blocks by default - then this part is not a problem
  my $val = $DataQueue->dequeue();
  do_something($_,$val);
}
# We are done: The producers are no longer needed
kill @producers;

sub producer {
   while(1) {
      # How do I wait until the queue length is smaller than number of threads?
      wait_until(length of $DataQueue < $no_of_threads);
      $DataQueue->enqueue(compute_slow_value());
   }
}

但有更优雅的方式吗？我特别不确定如何以有效的方式完成wait_until部分。

Answer 1

这样的事可能会奏效：

my $DataQueue = Thread::Queue->new();

my @producers;
my $no_of_threads = 10;
for (1..$no_of_threads) {
  push @producers, threads->create(\&producer);
}
$DataQueue->limit = 2 * $no_of_threads;

for(<>) {
  # This blocks until $DataQueue->pending > 0
  my $val = $DataQueue->dequeue();
  do_something($_,$val);
}
# We are done: The producers are no longer needed
kill @producers;

sub producer {
   while(1) {
      # enqueue will block until $DataQueue->pending < $DataQueue->limit
      $DataQueue->enqueue(compute_slow_value());
   }
}

Perl线程：如何制作一个制作人？

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