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clock() function in C/C++

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  • Difficulty Level : Easy
  • Last Updated : 28 Sep, 2018
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The clock() function is defined in the ctime header file. The clock() function returns the approximate processor time that is consumed by the program. The clock() time depends upon how the operating system allocate resources to the process that’s why clock() time may be slower or faster than the actual clock.

Syntax:

clock_t clock( void );

Parameters: This function does not accept any parameter.

Return Value: This function returns the approximate processor time that is consumed by the program and on failure function returns -1.

Below program illustrates the implementation of clock() function:




// C++ program to demonstrate
// example of clock() function.
  
#include<bits/stdc++.h>
using namespace std;
  
int main ()
{
    float a;
    clock_t time_req;
  
    // Without using pow function
    time_req = clock();
    for(int i=0; i<200000; i++)
    {
        a = log(i*i*i*i);
    }
    time_req = clock()- time_req;
    cout << "Processor time taken for multiplication: "
        << (float)time_req/CLOCKS_PER_SEC << " seconds" << endl;
  
    // Using pow function
    time_req = clock();
    for(int i=0; i<200000; i++)
    {
        a = log(pow(i, 4));
    }
    time_req = clock() - time_req;
    cout << "Processor time taken in pow function: "
        << (float)time_req/CLOCKS_PER_SEC << " seconds" << endl;
  
    return 0;
}

Output:

Processor time taken for multiplication: 0.006485 seconds
Processor time taken in pow function: 0.022251 seconds
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