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Editor to share with you what the concept of Perl thread queue and semaphore is, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

Semaphore

The Thread::Semaphore package provides semaphore support for Perl threads. You can create your own semaphore and access resources synchronously through down and up operations. In fact, the down operation and the up operation correspond to the well-known P operation and V operation. From an internal implementation point of view, Thread::Semaphore is essentially a locked shared variable, nothing more than encapsulating the locked shared variable into a Perl thread-safe package. Because the semaphore does not have to be bound to any variable, it is very flexible and can be used to control any data structure and program behavior you want to synchronize. For example

Listing semaphores in 13.Perl threads

Usethreads; usethreads::shared; useThread::Semaphore; my$s=Thread::Semaphore- > new (); $s-> down (); # Poperation... $s-> up (); # Voperation

Essentially, a semaphore is a reference to a shared integer variable. By default, it has an initial value of 1 minus its value by 1 minus its value by 1 minus 1 by adding 1 to its value. Of course, you can also customize the initial value of the semaphore and the change of the semaphore each time up or down is operated. For example

Listing semaphores in 14.Perl threads

Usethreads; useThread::Semaphore; my$s=Thread::Semaphore- > new (5); printf ("s =". ${$s}. "\ n"); # scut5 $s-> down (3); printf ("s =". ${$s}. "\ n"); # saw2... $s-> up (4); printf ("s =". ${$s}. "\ n"); # scut6

Perl thread queue

The Thread::Queue package provides Perl thread-safe queue support for Perl threads. Similar to semaphores, Thread::Queue encapsulates a shared queue for synchronous access through a lock mechanism into a Perl thread-safe package and provides a unified interface. In some cases, Thread::Queue can greatly simplify the difficulty and cost of communication between Perl threads. For example, in the producer-consumer model, producers can constantly do enqueue operations on the Perl thread queue, while consumers only need to do dequeue operations on the Perl thread queue, which simply realizes the synchronization between producers and consumers.

For example

Listing 15. Use of Perl thread queues in the producer-consumer model

#! / usr/bin/perl # usethreads; useThread::Queue; my$q=Thread::Queue- > new (); subproduce {my$name=shift; while (1) {my$r=int (rand (100)); $Q-> enqueue ($r); printf ("$nameproduce$r\ n"); sleep (int (rand (3));} subconsume {my$name=shift; while (my$r=$q- > dequeue ()) {printf ("consume$r\ n");} my$producer1=threads- > create (\ & produce, "producer1") My$producer2=threads- > create (\ & produce, "producer2"); my$consumer1=threads- > create (\ & consume, "consumer2"); $producer1- > join (); $producer2- > join (); $consumer1- > join ()

Other useful non-core packages

Everything discussed earlier in this article is within the scope of the Perl thread core package. In fact, there are other non-core packages related to Perl threads on CPAN, which often bring great convenience to the use of Perl threads. Here we choose two to introduce them a little bit.

The Thread::Pool package allows you to create a group of Perl threads in the program to perform multiple similar tasks. For example, when you want to create a multi-Perl threaded program to verify that all 1000 ip addresses can ping, the Thread::Pool package can bring you convenience.

The Thread::RWLock package provides lock mechanism support for read and write operations in Perl threads. For example, when you have multiple reader and writerPerl threads to access one or more files together, the Thread::RWLock package can bring you convenience.

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