multithreading

问题 I'm confused of user/kernel thread and mode/context switch (Platform: Linux) I have two linked questions. (1) Is the below sentence right? If I make a system call, then mode switch (user mode to kernel mode) will occur and eventually switching from user thread to kernel thread happens. Since system call can only be executed in kernel thread, I think mode switch must occur the switching from the user thread to kernel thread. (2) Then, what we call the overhead of mode switching is that

问题 I want to use fftw3 in threads. But the code pasted at http://codepad.org/lIjdGF5z causes "double free or corruption" error. How to call fftw3 routines in threads properly. Thanks! You can compile the code through command "g++ test.cpp -lfftw3_threads -lfftw3 -lboost_thread" 回答1: I believe the call to fftw_plan_dft_2d is not reentrant, meaning that it can't be called in multiple threads simultaneously, even if you are creating different plans. The only fftw functions that are thread-safe are

问题 I'm using multi thread inside my program in python. I've got 3 queues. In one of them I'm inserting data to postgres database. But before, I need to check if in the database already exists row with specific domain name. So I've got: class AnotherThread(threading.Thread): def __init__(self, another_queue): threading.Thread.__init__(self) self.another_queue = another_queue def run(self): while True: chunk = self.another_queue.get() if chunk is not '': dane = chunk[0].split(',',2) cur.execute(

问题 First of all, I've decided to make my class blocking (to make it easier for the consumer to use - but maybe more tedious for me to write). As opposed to having the consumer define asynchronous callbacks. Is this a good design pattern? This way, a user can get expected behaviour, but implement their own multi-threading if they're dissatisfied with how long the thread's blocked for. I've got a constructor that sets a final field in a class, based on the result of an async callback: class

问题 So I got into a debate whether multicore CPU allows parallel execution of separate processes. As far as I understand, each core allows executing different threads but they all have to belong to one process. Or am I wrong? My reasoning is that, while each core has separate set of registers and L1/L2 cache (depending on hardware), they all have to share other stuff like L3 cache or TLB (I don't have a lot of knowledge about cpu architecture, so feel free to correct me). I tried searching for an

问题 So I got into a debate whether multicore CPU allows parallel execution of separate processes. As far as I understand, each core allows executing different threads but they all have to belong to one process. Or am I wrong? My reasoning is that, while each core has separate set of registers and L1/L2 cache (depending on hardware), they all have to share other stuff like L3 cache or TLB (I don't have a lot of knowledge about cpu architecture, so feel free to correct me). I tried searching for an

问题 I have an application that i wrote that does a few heavy tasks, in which i display a Task Form. This task form shows the current progress, as well as Status text that is set within the heavy tasks thread. The issue I'm coming across right now is that My Invoke call (The UpdateStatus method) is getting called before the form actually has time to display itself, and starts throwing exceptions. Here is my form: public partial class TaskForm : Form { const int WM_SYSCOMMAND = 0x0112; const int SC

问题 I have an application that i wrote that does a few heavy tasks, in which i display a Task Form. This task form shows the current progress, as well as Status text that is set within the heavy tasks thread. The issue I'm coming across right now is that My Invoke call (The UpdateStatus method) is getting called before the form actually has time to display itself, and starts throwing exceptions. Here is my form: public partial class TaskForm : Form { const int WM_SYSCOMMAND = 0x0112; const int SC

问题 I am new to python and threading. I am trying to run multiple threads at a time. Here is my basic code : import threading import time threads = [] print "hello" class myThread(threading.Thread): def __init__(self,i): threading.Thread.__init__(self) print "i = ",i for j in range(0,i): print "j = ",j time.sleep(5) for i in range(1,4): thread = myThread(i) thread.start() While 1 thread is waiting for time.sleep(5) i want another thread to start. In short, all the threads should run parallel. 回答1

问题 There is something wrong with my code below. I am getting multiple instances of the same singleton class when calling it from multiple threads from the same process. I am expecting the program should print "Creating instance" only once but it is printing 3 times(i.e. per thread). package SingleTon; class SingleTon implements Runnable { String name; int salary; private static SingleTon singleTonInstance; SingleTon() { } public static SingleTon getInstance() { if (singleTonInstance == null) {