Question

Okay, so I’ve got some C code to perform a mathematical operation which could, pretty much, take any length of time (depending on the operands supplied to it, of course). I was wondering if there is a way to register some kind of method which will be called every n seconds which can analyse the state of the operation, i.e. what iteration it is currently at, possibly using a hardware timer interrupt or something?

The reason I ask this is because I know the common way to implement this is to be keeping track of the current iteration in a variable; say, an integer called progress and have an IF statement like this in the code:

if ((progress % 10000) == 0)
    printf("Currently at iteration %d\n", progress);

but I believe that a mod operation takes a relatively long time to execute, so the idea of having it inside a loop which will be ran many, many times scares me, from an optimisation point of view.

So I get the feeling that having an external way of signalling a progress print is nice and efficient. Are there any great ways to perform this, or is the simple ‘mod check’ the best (in terms of optimising)?

Answer 1

I’d go with the mod check, but maybe with subtractions instead 🙂

icount = 0;
progress = 10000;
/* ... */
    if (--progress == 0) {
        progress = 10000;
        printf("Currently at iteration %d0000\n", ++icount);
    }
/* ... */