Thread: time.h

It could very well be that, waiting for getchar() doesn't need any clocks, so your clock counter isn't incremented at all and thus giving the same result independent of how long you wait to press enter.

Originally Posted by KONI

It could very well be that, waiting for getchar() doesn't need any clocks, so your clock counter isn't incremented at all and thus giving the same result independent of how long you wait to press enter.

KONI, you might just be right! ....
I decided to add this, before the getchar();

like,

Code:

while(x<1000000)
     x++;

and finally it wasn't 0...but was like 0.09..
Btw, (start-stop)/CLOCKS_PER_SEC should be in seconds right??

Originally Posted by wuzzo87

KONI, you might just be right! ....
I decided to add this, before the getchar();

like,

Code:

while(x<1000000)
     x++;

and finally it wasn't 0...but was like 0.09..
Btw, (start-stop)/CLOCKS_PER_SEC should be in seconds right??

(stop-start) is clocks difference ... and guess what happens when you divide it by clocks_per_SEC(OND)

Originally Posted by quzah

That's what it seems like to me. The only way I can get it to change is by causing a loop to do something inbetween the prompts. Otherwise, it doesn't ever increment.

The clock doesn't tick when the process is sleeping. Calling sleep() or waiting for 45 minutes for keyboard input isn't going to increment the clock at all. I can't believe people are arguing over printf() format specifiers...

But the funny thing is,
I did a timing for a mergesort program, and it always results in 0 time interval..
I used a 'double' and %g for printing.

Could it be that the sorting happens too fast?
Even for 1000 items it prints 0 time interval....

i was going to say maybe your computer is just really fast.. but a value of 0 would mean the CPU didnt spend any time on the operation, correct?

can you post your code?

Originally Posted by nadroj

i was going to say maybe your computer is just really fast.. but a value of 0 would mean the CPU didnt spend any time on the operation, correct?

can you post your code?

Here's it:

Code:

int main(int argc, char **argv)
{
        int array[100];
        int item,j, i=0;
        int *comp = malloc(sizeof(int));
        int comp_result;
        clock_t start, stop;
        double t;

        while(scanf("%d", &item) > 0)
        {
                array[i] = item;
                i++;
        }

        start = clock();

        sort(array,i,comp);

        stop = clock();

        t = (double)(stop-start)/(double)(CLOCKS_PER_SEC);

        comp_result = *comp;

        for(j=0; j < i; j++)
                printf("%d ", array[j]);

        printf("\n");
        printf("%d comparisons made\n", comp_result);
        printf("Time taken : %.10g\n", t);


        return 0;
}

void sort(int array[],int size, int *comp)
{
        int b[100];
        int n=size;
        naturalmergesort(array, b, n, comp);
}

static bool mergeruns(int a[], int b[], int n, int *comp)
{
        int i=0, k=0, x;
        bool asc=true;

        while (i<n)
        {
            k=i;
            do x=a[i++]; while (i<n && x<=a[i]);
            while (i<n && x>=a[i]) x=a[i++];
            merge (a, b, k, i-1, asc, comp);
            asc=!asc;
        }
        return k==0;
}


void merge(int a[], int b[], int lo, int hi, bool asc, int *comp)
{
        int l = lo; int r = hi;
        int k=asc ? l : r;
        int c=asc ? 1 : -1;
        int i=lo, j=hi;
        int comparisons = 0;

        while (i<=j)
        {
            if (a[i]<=a[j])
            {
                b[k]=a[i++];
                comparisons++;
            }
            else
            {
                b[k]=a[j--];
                comparisons++;
            }
            k+=c;
        }
        *comp = comparisons;
        /*printf("%d comparisons made\n", comparisons);*/
}


void naturalmergesort(int a[], int b[], int n, int *comp)
{
        while (!mergeruns(a, b, n, comp) & !mergeruns(b, a, n, comp));
}

There's another one for sorting structs, but it's rather lengthy...

I used the shell command 'time', with 15 numbers,

said, 0:07.80elapse 0%CPU

My version of mergesort only displays a result starting from 15k upwards. I guess the process is probably too fast to be displayed with 6 decimal places.

Originally Posted by nadroj

@wuzzo87:

since your using 'bool', are you writing a C++ program? or have you included or defined whatever you need to so you can use 'bool'? notice you have a memory leak as you call 'malloc' without a corresponding 'free' on the variable.

woops...forgot to add the free() ...again...
Anyway, i've added the <stdbool.h> header to implement bools in C....