shared-state | 易学教程

Sharing static members between template instantiations? (impossible?)

阅读更多关于 Sharing static members between template instantiations? (impossible?)

问题 I am doing something that is probably silly, but it would be nice if it worked. I am attempting to specialize types in a way that I need my own lookup structure that is essentially global (but ideally encapsulated as a class variable), but I want the objects to be type safe, so they are parameterized. Consequently, I have, essentially template<class T, int N> class SpecialArray { //... private: static map<string, internal_t> lookupTable } and for whatever reason, I didn't think until such

Using Python's multiprocessing.pool.map to manipulate the same integer

阅读更多关于 Using Python's multiprocessing.pool.map to manipulate the same integer

问题 Problem I'm using Python's multiprocessing module to execute functions asynchronously. What I want to do is be able to track the overall progress of my script as each process calls and executes def add_print . For instance, I would like the code below to add 1 to total and print out the value ( 1 2 3 ... 18 19 20 ) every time a process runs that function. My first attempt was to use a global variable but this didn't work. Since the function is being called asynchronously, each process reads

How can I provide shared state to my Flask app with multiple workers without depending on additional software?

阅读更多关于 How can I provide shared state to my Flask app with multiple workers without depending on additional software?

问题 I want to provide shared state for a Flask app which runs with multiple workers, i. e. multiple processes. To quote this answer from a similar question on this topic: You can't use global variables to hold this sort of data. [...] Use a data source outside of Flask to hold global data. A database, memcached, or redis are all appropriate separate storage areas, depending on your needs. (Source: Are global variables thread safe in flask? How do I share data between requests?) My question is on

Two threads using a same variable

阅读更多关于 Two threads using a same variable

问题 I have two threads: 'main' and 'worker', and one global variable bool isQuitRequested that will be used by the main thread to inform worker , when it's time to quit its while loop (something like this: while(isQuitRequested == false) { ... do some stuff ... } ) Now, I'm a bit concerned... Do I need to use some kind of mutex protection for isQuitRequested , considering that only one thread ( main ) performs isQuitRequested = true operation, and the other ( worker ) just performs checking and

Two threads using a same variable

阅读更多关于 Two threads using a same variable

I have two threads: 'main' and 'worker', and one global variable bool isQuitRequested that will be used by the main thread to inform worker , when it's time to quit its while loop (something like this: while(isQuitRequested == false) { ... do some stuff ... } ) Now, I'm a bit concerned... Do I need to use some kind of mutex protection for isQuitRequested , considering that only one thread ( main ) performs isQuitRequested = true operation, and the other ( worker ) just performs checking and nothing else? I have read What could happen if two threads access the same bool variable at the same

Using Python's multiprocessing.pool.map to manipulate the same integer

阅读更多关于 Using Python's multiprocessing.pool.map to manipulate the same integer

Problem I'm using Python's multiprocessing module to execute functions asynchronously. What I want to do is be able to track the overall progress of my script as each process calls and executes def add_print . For instance, I would like the code below to add 1 to total and print out the value ( 1 2 3 ... 18 19 20 ) every time a process runs that function. My first attempt was to use a global variable but this didn't work. Since the function is being called asynchronously, each process reads total as 0 to start off, and adds 1 independently of other processes. So the output is 20 1 's instead

How to share a string amongst multiple processes using Managers() in Python?

阅读更多关于 How to share a string amongst multiple processes using Managers() in Python?

I need to read strings written by multiprocessing.Process instances from the main process. I already use Managers and queues to pass arguments to processes, so using the Managers seems obvious, but Managers do not support strings : A manager returned by Manager() will support types list, dict, Namespace, Lock, RLock, Semaphore, BoundedSemaphore, Condition, Event, Queue, Value and Array. How do I share state represented by a string using Managers from the multiprocessing module? Bengt multiprocessing's Managers can hold Values which in turn can hold instances of the type c_char_p from the

How to share a string amongst multiple processes using Managers() in Python?

阅读更多关于 How to share a string amongst multiple processes using Managers() in Python?

问题 I need to read strings written by multiprocessing.Process instances from the main process. I already use Managers and queues to pass arguments to processes, so using the Managers seems obvious, but Managers do not support strings: A manager returned by Manager() will support types list, dict, Namespace, Lock, RLock, Semaphore, BoundedSemaphore, Condition, Event, Queue, Value and Array. How do I share state represented by a string using Managers from the multiprocessing module? 回答1: