multiprocess

multiprocess module vs multiprocessing module

不问归期 提交于 2021-01-29 13:43:33
问题 I have a function which I want to map to a list in parallel. I achieved the task by using multiprocess module. However, when I want to run this task with multiprocessing module, it seems that the processes has spawn but none of them start working. The function and configuration of multiprocess module is as follow: import pandas as pd my_file = pd.read_csv('my_file.txt') from datetime import date, timedelta start_dates = [] for i in range(17): today = date.today() - timedelta(days = i) start

Python‘最难’的问题——GIL问题

前提是你 提交于 2020-11-23 23:59:43
[TOC] 一、什么是GIL GIL(解释器全局锁) 从名字上看能告诉我们很多东西,很显然,这是一个加在解释器上的全局(从解释器的角度看)锁(从互斥或者类似角度看)。 首先来看回顾一下什么是锁: 为什么加锁 由于多线程共享进程的资源和地址空间,因此,在对这些公共资源进行操作时,为了防止这些公共资源出现异常的结果,必须考虑线程的同步和互斥问题。 加锁的作用 1、用于非线程安全,2、控制一段代码,确保其不产生调度混乱。 GIL官方给出的解释 In CPython, the global interpreter lock, or GIL, is a mutex that prevents multiple native threads from executing Python bytecodes at once. This lock is necessary mainly because CPython’s memory management is not thread-safe. (However, since the GIL exists, other features have grown to depend on the guarantees that it enforces.) 在CPython中,全局解释器锁(global interpreter lock, GIL

Prometheus Python Client 多进程问题的解释与解决

吃可爱长大的小学妹 提交于 2020-10-02 20:08:35
本文描述基于 prometheus-client (0.8.0) 版本。 Client 存储数据的方法与问题 官方 client 用于存储数据(不管是什么 Metric 类型)使用的是一个 ValueClass 对象,默认情况下定义是: class MutexValue(object): """A float protected by a mutex.""" _multiprocess = False def __init__(self, typ, metric_name, name, labelnames, labelvalues, **kwargs): self._value = 0.0 self._lock = Lock() def inc(self, amount): with self._lock: self._value += amount def set(self, value): with self._lock: self._value = value def get(self): with self._lock: return self._value 使用这个对象而不是 float 的目的主要应该是为了在多线程情况下加锁。 显然这个值是不能在多进程场景下共享的,而多进程模式对于 Python 来说又是一种非常常用的模式,因此出现了一个

Python多进程与多线程编程及GIL详解

邮差的信 提交于 2020-04-27 20:57:02
介绍如何使用python的multiprocess和threading模块进行多线程和多进程编程。 Python的多进程编程与multiprocess模块 python的多进程编程主要依靠multiprocess模块。我们先对比两段代码,看看多进程编程的优势。我们模拟了一个非常耗时的任务,计算8的20次方,为了使这个任务显得更耗时,我们还让它sleep 2秒。第一段代码是单进程计算(代码如下所示),我们按顺序执行代码,重复计算2次,并打印出总共耗时。 import time import os def long_time_task(): print ( ' 当前进程: {} ' .format(os.getpid())) time.sleep( 2 ) print ( " 结果: {} " .format(8 ** 20 )) if __name__ == " __main__ " : print ( ' 当前母进程: {} ' .format(os.getpid())) start = time.time() for i in range(2 ): long_time_task() end = time.time() print ( " 用时{}秒 " .format((end-start))) 输出结果如下,总共耗时4秒,至始至终只有一个进程14236

Python3 多进程编程

六眼飞鱼酱① 提交于 2020-04-27 18:06:44
Python3 多进程编程(Multiprocess programming) 为什么使用多进程 具体用法 Python多线程的通信 进程对列Queue 生产者消费者问题 JoinableQueue Queue实例 管道Pipe Python3 多进程编程(Multiprocess programming) 为什么使用多进程   python中的多线程其实并不是真正的多线程,不能充分地使用多核CPU的资源,此时需要使用需要使用多进程解决问题。 具体用法   Python中的多进程是通过 multiprocessing 模块来实现的,和多线程的 threading.Thread 类似,利用 multiprocessing.Process 来创建一个进程对象。进程对象的方法和线程对象的方法类似,也有start(), join()等。 直接启用 <details> <summary>代码实例</summary> import multiprocessing from time import sleep def clock(interval): i = 0 while i<5: i += 1 print(f"Run >>> {i}") sleep(interval) print("Ending!") if __name__ == '__main__': p =

Python memory profiler 上手实践

岁酱吖の 提交于 2020-04-12 07:31:16
为什么 相比起 C ,Python 有自己的内存管理,不需开发者自己管理内存。虽然方便,但有时候,我们可能会遇到内存占用过高,内存泄漏,甚至 OOM 的情况。这时,就需要我们做内存诊断,了解自己的代码:内存主要被分配在哪里,是否有无法释放的内存,又有多少内存会很快被释放,进程在高峰时占用多少内存,在低谷时占用多少内存。 怎么办 要了解进程的内存使用情况,我们可能首先会想到使用 TOP 命令,查看进程内存的使用情况。TOP 命令能够实时查看到进程对各种资源的使用情况,也是我们经常会使用的Linux命令。而在 Python 中,通过 psutil 模块也能很好的获取到这些信息。 这两个工具十分的强大,但是也很基础。TOP命令不方便从更多的维度诊断问题,比如难以从时间维度诊断内存,只能统计当前整个进程的内存使用情况,与代码脱离。而 psutil 十分强大,可以和代码结合,但是对逻辑代码侵入性太强,比如想在某个函数前后统计内存的使用情况,就需要在原有代码的基础上插桩,产生不必要的耦合,而不侵入逻辑代码则又和使用命令行没有太大区别。 这个时候,有经验的朋友可能会想到 line_profiler。line_profiler 是用于对函数进行逐行分析的模块,只需要通过装饰器,就可以计算出函数内每一行代码的执行时间,以提供时间维度的性能诊断。那么在内存维度上,是不是也有类似的模块呢?bingo

Python / Celery : how can I kill subtasks when killing a parent task?

♀尐吖头ヾ 提交于 2020-03-01 05:43:27
问题 Context I've created a Django application that is calling a celery task which in turns spawn other tasks and wait for them to be finished. Here's the workflow : 1) The main python/django code start a celery task in the background 2) The celery task process some code and then start a celery group of differents tasks and wait for them to be ready 3) every task of the group then spawn another group of subtasks in the same way and wait for them to finish It works well (although I'm a begginer and

Python / Celery : how can I kill subtasks when killing a parent task?

坚强是说给别人听的谎言 提交于 2020-03-01 05:43:25
问题 Context I've created a Django application that is calling a celery task which in turns spawn other tasks and wait for them to be finished. Here's the workflow : 1) The main python/django code start a celery task in the background 2) The celery task process some code and then start a celery group of differents tasks and wait for them to be ready 3) every task of the group then spawn another group of subtasks in the same way and wait for them to finish It works well (although I'm a begginer and

Python: How can I check the number of pending tasks in a multiprocessing.Pool?

放肆的年华 提交于 2020-02-18 05:01:48
问题 I have a small pool of workers (4) and a very large list of tasks (5000~). I'm using a pool and sending the tasks with map_async(). Because the task I'm running is fairly long, I'm forcing a chunksize of 1 so that one long process can't hold up some shorter ones. What I'd like to do is periodically check how many tasks are left to be submitted. I know at most 4 will be active, I'm concerned with how many are left to process. I've googled around and I can't find anybody doing this. Some simple

PyQt5 and multiprocessing - multiple processes create multiple windows incorrectly

匆匆过客 提交于 2020-01-15 09:51:27
问题 Trying to implement multiprocessing within a PyQt5 GUI framework to process multiple files in a parallel process, preferably in a QThread() background. Running the code below seems to create the multiple processes but has additional issue that multiple GUI windows appear and everything seems locked out at that point. import multiprocess as mp from PyQt5.QtWidgets import QMainWindow class MyApp(QMainWindow, myUiMainWindow): def __init__(self): super(self.__class__, self).__init() self.setupUI