I can go into a lot of detail about this but first, go read “1500 archers” http://www.gamasutra.com/view/feature/3094/1500_archers_on_a_288_network_.php and this will answer many of your questions. Here’s a summary: First, most games use UDP due to the real-time nature of the game. THe game loop looks something like this: read network data do client-side predictions and … Read more
Exceptions are now well-handled, and the strategies used to implement them make them in fact faster than testing return code, because their cost (in terms of speed) is virtually null, as long as you do not throw any. However they do cost: in code-size. Exceptions usually work hand in hand with RTTI, and unfortunately RTTI … Read more
At Galois we use Haskell for two things: Soft real time (OS device layers, networking), where 1-5 ms response times are plausible. GHC generates fast code, and has plenty of support for tuning the garbage collector and scheduler to get the right timings. for true real time systems EDSLs are used to generate code for … Read more
Is there a name for Google’s solution for real-time updates in Drive (such as “long polling” or “sockets”)? It didn’t have a name until now. I’ll call it “no-polling,” to contrast with polling and long-polling. With polling, the client periodically sends queries for new data. With long-polling, the client queries for data, and the server … Read more
This worked for me: $cmd = “ping 127.0.0.1”; $descriptorspec = array( 0 => array(“pipe”, “r”), // stdin is a pipe that the child will read from 1 => array(“pipe”, “w”), // stdout is a pipe that the child will write to 2 => array(“pipe”, “w”) // stderr is a pipe that the child will write … Read more
In the context of realtime systems, there is more to determinism than a repeatable “execution path”. Another required property is that timing of key events is bounded. In hard realtime systems, an event that occurs outside its allowed time interval (either before the start of that interval, or after the end) represents a system failure. … Read more
I did an experiment to nail this down, as follows: process1: RT priority = 40, CPU affinity = CPU 0. This process “spins” for 10 seconds so it won’t let any lower-priority process run on CPU 0. process2: RT priority = 39, CPU affinity = CPU 0. This process prints a message to stdout every … Read more
Just for the sake of argument. Both are http request (xhr), and its at least partially untrue it uses more server resources (depends totally on technology, will explain later). Short polling. Lot of request that are processed as they come on server. Creates a lot of traffic (uses resources, but frees them as soon as … Read more
So, to begin with, I put my project on github, if you want access to the full code: https://github.com/jdutheil/nodePHP It is a very simple example project: a web chat. You just have an author and message, and when you press send it is saved in a mysql database. The idea is to send real time … Read more