Quote:Original post by ghetalion
I'm sorry... threads? My understanding of programming is that there is no such thing as paralell processing.
The delay may or may not be nessecary.. and sometimes the opposite will be needed... due to limitations of... say.. quantum mechanics, there is no such thing as a SpeedUp() function. The solution needs to be dynamic and adaptable to the situation.
Well, your understanding of programming is flawed by not having an idea of threading, but I won't go there since PHP doesn't really have a facility for threading... yet.
Meanwhile, the sleep is nessicary if you want to sync the Event Hander's loop to realtime. You don't have anything more to process, so let the loop idle for however much time adds up to the three seconds that the Event Handler's supposed to activate on anyways.
Your "Blueshifting/Redshifting" problem is caused by the event loop's intervals terminating too early or too late; if you want it to happen every 3 seconds, you must have a way of telling the computer to stop after 3 seconds, and you must have a way of telling the computer how to cope with extra time. This is where sleep and a good timing function come in. Sleep() when you have extra time, peek on the timer before doing anything you know takes a bit of time, if there's even a question that the event will put you over-time on your processing budget, simply delay processing the event until the next clock interval and sleep away the rest of the time. (keep in mind that peeking on the timer will also cost you time, so you shouldn't simply do it before every single function call, just the ones you know are slow such as a database query or an image blitting function).
--- top of event handler's inner loop ---
if (($preEventTime + 3) > getTime()) {
//go ahead and keep the loop running, we still have time.
if ((getTime() + .5) >= $preEventTime)
{
//skip processing this event, it's simply going to take too long
// EDIT: If you're using a priority queue, instead of continuing the loop,
// break here instead, and Sleep() the rest of the time until the 3 seconds
// are up. How do you know if this is ineffecient? Well, if you're spending
// more than half of your time asleep, you know something's wrong.
// Perhaps your event simply can't be processed in a timely manner (3 secs)?
continue; //move on to the next event in the loop
} else {
doSlowQuery();
}
} else {
//log the fact that you've spent too much time
$log .= "too little time\n";
//break out of the inner loop
break (2);
}
--- bottom of event handler's inner loop ---
Believe it or not, even big fancy games coded by game studios will use this to get around timing issues. If you want something to work in real time, you have to cope with the computer's abilities. Someone with a really fast computer's going to be able to process events much, much quicker than my 486 in the closet. Sleep() may be "wasting", but it allows for events to occur at the same time on both the ultra new machine, and the 486.
So really, just add the sleep and peek on the timer when you need to. It's the fix to the problem you're having, even if you don't understand why its neccesary now. Continuing to argue that you don't want to do it is only going to drive people on this site crazy (like the guy who couldn't figure out asin() is always going to be faster and more bugfree than his own implementation). Believe it or not, Sleep() is effecient programming if you want to do something in a timely manner, and its the reason modern processors have the nop ability. Think about it; if everything could run sychronous to realtime and not use sleep, who would? Why would the facility be left in the language?
[Edited by - ciroknight on January 2, 2006 6:34:20 AM]
