Question

I have an increasing integer value and want to find the average per second of that integer. I am aware that timers do not exist in C unless you do something specific and complicated [Im new to C] Is there a simpler way to do this? Preferably the value would reset when the calculation is made in order to not have such a large number in memory as this application will be running for a long time.

Answer 1

I think you will want to include time.h, and use some of its functions and structs (this is actually not a bad way of learning the basics of C). There is an explanation and a few examples here.

If you need sub-second accuracy I suggest you use clock_gettime(), which will give you nanosecond resolution.

Here is an example:

#include <stdio.h>
#include <time.h>

struct timespec diff(struct timespec start, struct timespec end);

int main()
{
    struct timespec time1, time2, timeDiff;
    int temp, i;

    // Get the start time
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time1);

    // Do some work
    for (i = 0; i< 242000000; i++)
        temp+=temp;

    // Get the end time
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time2);

    // Calculate the difference
    timeDiff = diff(time1,time2);

    printf("%d.%d\n", timeDiff.tv_sec, timeDiff.tv_nsec);
    return 0;
}

struct timespec diff(struct timespec start, struct timespec end)
{
    struct timespec temp;
    if ((end.tv_nsec-start.tv_nsec)<0) {
        temp.tv_sec = end.tv_sec-start.tv_sec-1;
        temp.tv_nsec = 1000000000+end.tv_nsec-start.tv_nsec;
    } else {
        temp.tv_sec = end.tv_sec-start.tv_sec;
        temp.tv_nsec = end.tv_nsec-start.tv_nsec;
    }
    return temp;
}

You will need to compile with something like:

gcc -o timetest timetest.c -lrt

The -lrt part of the command tells the C linker to link to the Realtime library, which contains the definition of clock_gettime().