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mswift · Nov 28th, 2004, 11:57 AM

I am using a book called Teach yourself C++ Third Edition.
On Exercise #4 on page 38 it calls for a "delay loop" to be used. The purpuse of the exercise is to demonstrate function overloading, something I understand, but what is a delay loop?

Eggbert · Nov 28th, 2004, 12:03 PM

>what is a delay loop?

(Toggle Plain Text)

for ( int i = 0; i < SOME_BIG_NUMBER; i++ )
 ; // Eat up CPU cycles

This is far from the best way to implement a delay, but it should work for your purposes.

kurifu · Nov 28th, 2004, 3:14 PM

Actually it does not mean that you have to eat up CPU cycles in a delay loop... is just means that there is code in there that is causing a significant delay between iterations, most likely from a sleep command which forces the proecessor to not do anything for a specified period of time in milliseconds.

(Toggle Plain Text)

for(;; )
{
   ...execute some code...
   Sleep( 100 );
}

is a good example of a delay loop. Delay loops are very commonly used in multi-threading and server-client applications, as well as many other applications. Sometimes you can have a process trying to pol for input from a network socket or a local device, the problem is your processor will run a polling loop as fast as it can unless you forece it to slow down... you do this with sleep.

On another interesting not... Sleep( 0 ) is usually a valid statement, and it does not execute a CPU wait for 0 milliseconds, what this usually does is it instructs the operating system to end the timeslice for the process that is running and execute other timeslices for other processes and threads before returning, this is typically a very effective way of managing the polling loop issue.

Nov 28th, 2004, 12:03 PM	#2
Eggbert Professional Programmer Join Date: Nov 2004 Posts: 250 Rep Power: 4	>what is a delay loop? (Toggle Plain Text) for ( int i = 0; i < SOME_BIG_NUMBER; i++ ) ; // Eat up CPU cycles for ( int i = 0; i < SOME_BIG_NUMBER; i++ ) ; // Eat up CPU cycles This is far from the best way to implement a delay, but it should work for your purposes.

Nov 28th, 2004, 3:14 PM	#3
kurifu Expert Programmer Join Date: Jul 2004 Location: Halifax, Nova Scotia (Canada) Posts: 784 Rep Power: 5	Actually it does not mean that you have to eat up CPU cycles in a delay loop... is just means that there is code in there that is causing a significant delay between iterations, most likely from a sleep command which forces the proecessor to not do anything for a specified period of time in milliseconds. (Toggle Plain Text) for(;; ) { ...execute some code... Sleep( 100 ); } for(;; ) { ...execute some code... Sleep( 100 ); } is a good example of a delay loop. Delay loops are very commonly used in multi-threading and server-client applications, as well as many other applications. Sometimes you can have a process trying to pol for input from a network socket or a local device, the problem is your processor will run a polling loop as fast as it can unless you forece it to slow down... you do this with sleep. On another interesting not... Sleep( 0 ) is usually a valid statement, and it does not execute a CPU wait for 0 milliseconds, what this usually does is it instructs the operating system to end the timeslice for the process that is running and execute other timeslices for other processes and threads before returning, this is typically a very effective way of managing the polling loop issue. __________________ Clifford Matthew Roche <geek@cliffordroche.com> Web Hosting: http://www.crd-hosting.com Consulting: http://www.crdev-consulting.com

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Nov 28th, 2004, 11:57 AM	#1
mswift Newbie Join Date: Nov 2004 Posts: 5 Rep Power: 0	I am using a book called Teach yourself C++ Third Edition. On Exercise #4 on page 38 it calls for a "delay loop" to be used. The purpuse of the exercise is to demonstrate function overloading, something I understand, but what is a delay loop?

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Delay Loop