gil

Python GIL and multithreading

时间秒杀一切 提交于 2019-12-04 13:24:17
问题 I would like to separate my sigle-thread application to number of working threads. Just 1 question - what about performance of this action? If GIL prevents python from executing more than 1 thread at the time will I have any profit? Another point (from c/c++ point of view) - as I know each thread, anyway, can be only executed exclusively, so in the lower level than python interpreter I have the same limitation. Summary: Will the the python threads have lesser efficiency that 'native' thread

Thread-local arrays in cython's prange without huge memory allocation

梦想的初衷 提交于 2019-12-04 06:19:31
问题 I have some independent computations I would like to do in parallel using Cython. Right now I'm using this approach: import numpy as np cimport numpy as cnp from cython.parallel import prange [...] cdef cnp.ndarray[cnp.float64_t, ndim=2] temporary_variable = \ np.zeros((INPUT_SIZE, RESULT_SIZE), np.float64) cdef cnp.ndarray[cnp.float64_t, ndim=2] result = \ np.zeros((INPUT_SIZE, RESULT_SIZE), np.float64) for i in prange(INPUT_SIZE, nogil=True): for j in range(RESULT_SIZE): [...] temporary

Improving Python execution speed with parallel threads

时光总嘲笑我的痴心妄想 提交于 2019-12-04 02:23:58
问题 Let's say I have this sample code: x = foo1(something1) y = foo2(something2) z = max(x, y) I want to improve the execution time of this code by using threads (hope it helps isn't it?). I'd like to keep things as simple as possible so basically what I'd like to do is creating two threads working at the same time which compute respectively foo1 and foo2 . I'm reading something about threads but I found it a little tricky and I can't lose too much time in it just for doing such a simple thing.

A thread-safe memoize decorator

早过忘川 提交于 2019-12-03 16:19:40
I'm trying to make a memoize decorator that works with multiple threads. I understood that I need to use the cache as a shared object between the threads, and acquire/lock the shared object. I'm of course launching the threads: for i in range(5): thread = threading.Thread(target=self.worker, args=(self.call_queue,)) thread.daemon = True thread.start() where worker is: def worker(self, call): func, args, kwargs = call.get() self.returns.put(func(*args, **kwargs)) call.task_done() The problem starts, of course, when I'm sending a function decorated with a memo function (like this ) to many

Why Python is not better in multiprocessing or multithreading applications than Java?

丶灬走出姿态 提交于 2019-12-03 13:32:10
Since Python has some issues with GIL, Java is better for developing multiprocessing applications. Could you please justify the exact reasoning of java's effective processing than python in your way? Joachim Sauer The biggest problem in multithreading in CPython is the Global Interpreter Lock (GIL) (note that other Python implementations don't necessarily share this problem!) The GIL is an implementation detail that effectively prevents parallel (simultaneous) execution of separate threads in Python. The problem is that whenever Python byte code is to be executed, then the current thread must

Why are numpy calculations not affected by the global interpreter lock?

不打扰是莪最后的温柔 提交于 2019-12-03 10:27:22
问题 I'm trying to decide if I should use multiprocessing or threading, and I've learned some interesting bits about the Global Interpreter Lock. In this nice blog post, it seems multithreading isn't suitable for busy tasks. However, I also learned that some functionality, such as I/O or numpy, is unaffected by the GIL. Can anyone explain why, and how I can find out if my (probably quite numpy-heavy) code is going to be suitable for multithreading? 回答1: Many numpy calculations are unaffected by

Python GIL and multithreading

北城余情 提交于 2019-12-03 08:25:07
I would like to separate my sigle-thread application to number of working threads. Just 1 question - what about performance of this action? If GIL prevents python from executing more than 1 thread at the time will I have any profit? Another point (from c/c++ point of view) - as I know each thread, anyway, can be only executed exclusively, so in the lower level than python interpreter I have the same limitation. Summary: Will the the python threads have lesser efficiency that 'native' thread in part of task switching? Don't worry about the GIL. Depending on the kinds of things your program does

Is the Python GIL really per interpreter?

可紊 提交于 2019-12-03 06:06:54
I often see people talking that the GIL is per Python Interpreter (even here on stackoverflow). But what I see in the source code it seems to be that the GIL is a global variable and therefore there is one GIL for all Interpreters in each python process. I know they did this because there is no interpreter object passed around like lua or TCL does, it was just not designed well in the beginning. And thread local storage seems to be not portable for the python guys to use. Is this correct? I had a short look at the 2.4 version I'm using in a project here. Had this changed in later versions,

Using a dictionary in Cython , especially inside nogil

夙愿已清 提交于 2019-12-03 03:57:01
问题 I am having a dictionary, my_dict = {'a':[1,2,3], 'b':[4,5] , 'c':[7,1,2]) I want to use this dictionary inside a Cython nogil function . So , I tried to declare it as cdef dict cy_dict = my_dict Up to this stage is fine. Now I need to iterate over the keys of my_dict and if the values are in list, iterate over it. In Python , it is quite easy as follows: for key in my_dict: if isinstance(my_dict[key], (list, tuple)): ###### Iterate over the value of the list or tuple for value in list: ## Do

What is a global interpreter lock (GIL)?

匿名 (未验证) 提交于 2019-12-03 02:44:02
可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效,请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: What is a global interpreter lock and why is it an issue? A lot of noise has been made around removing the GIL from Python, and I'd like to understand why that is so important. I have never written a compiler nor an interpreter myself, so don't be frugal with details, I'll probably need them to understand. 回答1: Python's GIL is intended to serialize access to interpreter internals from different threads. On multi-core systems, it means that multiple threads can't effectively make use of multiple cores. (If the GIL didn't lead to