low-latency | 易学教程

ZeroMQ Subscribers not receiving message from Publisher over an inproc: transport class

阅读更多关于 ZeroMQ Subscribers not receiving message from Publisher over an inproc: transport class

问题 I am fairly new to pyzmq . I am trying to understand inproc: transport class and have created this sample example to play with. It looks a Publisher instance is publishing messages but Subscriber instances are not receiving any. In case I move Subscriber instances into a separate process and change inproc: to a tcp: transport class, the example works. Here is the code: import threading import time import zmq context = zmq.Context.instance() address = 'inproc://test' class Publisher(threading

MQL4, Code layout for big EA

阅读更多关于 MQL4, Code layout for big EA

问题 It is mostly a theoretical question ( but example code is always welcome ). The real question is: how to correctly code the 'frame' of an EA that tests multiple scenarios from multiple custom indicators? The way I'm ( busy ) building an EA, is not very much focused on 1 strategy, but is gonna try to 'test' multiple strategies and 'picks' the most appropriate one. So I have created a few custom indicators, that are all returning an array of 'status data'. For example I have the following

Opening camera in multiple program in openCV

阅读更多关于 Opening camera in multiple program in openCV

问题 How can I open a single webcam in multiple programs written in openCV simultaneously. Btw I have attached 3 webcams and all are working fine in any single program of openCV , but why two program can't use them both, simultaneously? Is this a restriction or is there any workaround? 回答1: Yes, this is an intention to restrict Why? The conceptual view is related to the hardware control layer. Operating system assumes, there are some peripherals, that can be used on-demand, but keeps their context

Compiler optimization on marking an int unsigned?

阅读更多关于 Compiler optimization on marking an int unsigned?

问题 For an integer that is never expected to take -ve values, one could unsigned int or int. From a compiler perspective or purely cpu cycle perspective is there any difference on x86_64 ? 回答1: It depends. It might go either way, depending on what you are doing with that int as well as on the properties of the underlying hardware. An obvious example in unsigned int s favor would be the integer division operation. In C/C++ integer division is supposed to round towards zero , while machine integer

Deadlock when synchronizing two simple python3 scripts using 0mq (ZeroMQ)

阅读更多关于 Deadlock when synchronizing two simple python3 scripts using 0mq (ZeroMQ)

问题 I get this strange deadlock when I try to synchronize two python3 scripts using 0mq ( ZeroMQ ). The scripts run fine for several thousand iterations, but sooner or later they both stop and wait for each other. I am running both scripts from different CMD-Windows on Windows 7. I cannot figure out why such a deadlock is even possible . What can go wrong here? Script A: while (1): context = zmq.Context() socket = context.socket(zmq.REP) socket.bind('tcp://127.0.0.1:10001') msg = socket.recv() #

Deadlock when synchronizing two simple python3 scripts using 0mq (ZeroMQ)

阅读更多关于 Deadlock when synchronizing two simple python3 scripts using 0mq (ZeroMQ)

I get this strange deadlock when I try to synchronize two python3 scripts using 0mq ( ZeroMQ ). The scripts run fine for several thousand iterations, but sooner or later they both stop and wait for each other. I am running both scripts from different CMD-Windows on Windows 7. I cannot figure out why such a deadlock is even possible . What can go wrong here? Script A: while (1): context = zmq.Context() socket = context.socket(zmq.REP) socket.bind('tcp://127.0.0.1:10001') msg = socket.recv() # Waiting for script B to send done # ...................................................................

C++ Low-Latency Threaded Asynchronous Buffered Stream (intended for logging) – Boost

阅读更多关于 C++ Low-Latency Threaded Asynchronous Buffered Stream (intended for logging) – Boost

问题 Question : 3 while loops below contain code that has been commented out. I search for ("TAG1", "TAG2", and "TAG3") for easy identification. I simply want the while loops to wait on the condition tested to become true before proceeding while minimizing CPU resources as much as possible. I first tried using Boost condition variables, but there's a race condition. Putting the thread to sleep for 'x' microseconds is inefficient because there is no way to precisely time the wakeup. Finally, boost:

What is the fastest way to send data from one thread to another in C++?

阅读更多关于 What is the fastest way to send data from one thread to another in C++?

问题 I have tried an experiment where I built a simple Producer/Consumer program. They run in separate threads. The producer generates some data and the consumer picks it up in another thread. The messaging latency I achieved is approximately 100 nano seconds. Can anybody tell me if this is reasonable or are there significantly faster implementations out there? I'm not using locks ... just simple memory counters. My experiment is described here: http://tradexoft.wordpress.com/2012/10/22/how-to

USB: low latency (< 1ms) with interrupt transfer and raw HID

阅读更多关于 USB: low latency (< 1ms) with interrupt transfer and raw HID

问题 I have a project that requires reading an external IMU gyroscope data at regular interval and sending the data over to an Android phone. I am using a teensy 2.0 board to query the IMU via I2C and send it over USB using raw HID. I am using RawHID variable which is declared in usb_api.h of usb_rawhid of teensyduino. I have read that a full-speed USB using interrupt transfer can have a 1ms maximum latency and would like to achieve this 1ms maximum latency. I am not sure what to look for to

Why does TCP/IP on Windows7 take 500 sends to warm-up? ( w10,w8 proved not to suffer )

阅读更多关于 Why does TCP/IP on Windows7 take 500 sends to warm-up? ( w10,w8 proved not to suffer )

We are seeing a bizarre and unexplained phenomenon with ZeroMQ on Windows 7 , sending messages over TCP. ( Or over inproc , as ZeroMQ uses TCP internally for signalling, on Windows ). The phenomenon is that the first 500 messages arrive slower and slower, with latency rising steadily. Then latency drops and messages arrive consistently rapidly, except for spikes caused by CPU/network contention. The issue is described here: https://github.com/zeromq/libzmq/issues/1608 It is consistently 500 messages. If we send without a delay, then messages are batched so we see the phenomenon stretch over