timer1_v1.c

/*

    timer1_v1.c


    You can find all my C programs at Dragan Milicev's pastebin:

    https://pastebin.com/u/dmilicev

*/

#include <stdio.h>
#include <time.h>               // clock_t, clock(), CLOCKS_PER_SEC

int multiply(int n, int m)
{
    int ans = 0, count = 0;
    while (m)
    {
        if (m % 2 == 1)         // check for set bit and left
            ans += n << count;  // shift n, count times

        count++;                // increment of place value (count)
        m /= 2;
    }
    return ans;
}

int main(void)
{
    clock_t start_time, end_time;
    double elapsed_time;

    int i;
    unsigned sum=1, n=100000000;    // n is the number of terms

    start_time = clock();   // start measuring time
    for(i=1; i<=n; i++)
    {
        sum = i*10 + 1;
    }
    end_time = clock();     // end measuring time
    elapsed_time = (double)(end_time - start_time) / CLOCKS_PER_SEC;
    printf("\n 1. Classically, by multiplication ");
    printf("\n 1. sum = %u ", sum);
    printf("\n 1. elapsed_time =    %lf s \n", elapsed_time);


    start_time = clock();   // start measuring time
    for(i=1; i<=n; i++)
    {
        sum = (i << 3) + i + i + 1;
    }
    end_time = clock();     // end measuring time
    elapsed_time = (double)(end_time - start_time) / CLOCKS_PER_SEC;
    printf("\n 2. Using shift operator and addition ");
    printf("\n 2. sum = %u ", sum);
    printf("\n 2. elapsed_time =    %lf s \n", elapsed_time);


    start_time = clock();   // start measuring time
    for(i=1; i<=n; i++)
    {
        sum = (i << 3) + (i << 1) + 1;
    }
    end_time = clock();     // end measuring time
    elapsed_time = (double)(end_time - start_time) / CLOCKS_PER_SEC;
    printf("\n 3. Using shift operator ");
    printf("\n 3. sum = %u ", sum);
    printf("\n 3. elapsed_time =    %lf s \n", elapsed_time);


    start_time = clock();   // start measuring time
    for(i=1; i<=n; i++)
    {
        sum = multiply(i,10) + 1;
    }
    end_time = clock();     // end measuring time
    elapsed_time = (double)(end_time - start_time) / CLOCKS_PER_SEC;
    printf("\n 4. By calling the multiplication function ");
    printf("\n 4. sum = %u ", sum);
    printf("\n 4. elapsed_time =    %lf s \n", elapsed_time);


    start_time = clock();   // start measuring time
    unsigned ans = 0;
    int count = 0, m=10;
    for(i=1; i<=n; i++)
    {
        while (m)
        {
            if (m % 2 == 1)         // check for set bit and left
                ans += n << count;  // shift n, count times

            count++;                // increment of place value (count)
            m /= 2;
        }
        ans = ans + 1;
        count=0;
        m=10;
    }
    end_time = clock();     // end measuring time
    elapsed_time = (double)(end_time - start_time) / CLOCKS_PER_SEC;
    printf("\n 5. With code of multiplication function ");
    printf("\n 5. sum = %u ", sum);
    printf("\n 5. elapsed_time =    %lf s \n", elapsed_time);


    return(0);
}