My question is about the difference of the elapsed time according to the point.
For finding the largest portion of the total elapsed time when executing in my code, I used clock function.
source : calculating time elapsed in C++
First, I put the clock function at the start and end of the main function.
(Actually, there are some declaration of variables but I deleted them for readability of my questions). Then I think I will be able to measure the total elapsed time.
int main(){
using clock = std::chrono::system_clock;
using sec = std::chrono::duration<double>;
const auto before = clock::now();
...
std::cin >> a >> b;
lgstCommSubStr findingLCSS(a,b,numberofHT,cardi,SubsA);
const sec duration = clock::now() - before;
std::cout << "It took " << duration.count() << "s in main function" << std::endl;
return 0;
}
Second, I put the clock function at the class findingLCSS. This class is for finding longest common sub-string between two string. It is the class that actually do my algorithm. I write the code for finding it in its constructor. Therefore, when making this class, it returns longest common sub-string information. I think this elapsed time will be the actual algorithm running time.
public:
lgstCommSubStr(string a, string b, int numHT, int m, vector <int> ** SA):
strA(a), strB(b), hashTsize(numHT), SubstringsA(SA),
primeNs(numHT), xs(numHT),
A_hashValues(numHT), B_hashValues(numHT),
av(numHT), bv(numHT), cardi(m)
{
using clock = std::chrono::system_clock;
using sec = std::chrono::duration<double>;
const auto before = clock::now();
...
answer ans=binarySearch(a,b, numHT);
std::cout << ans.i << " " << ans.j << " " << ans.length << "\n";
const sec duration = clock::now() - before;
std::cout << "It took " << duration.count() << "s in the class" << std::endl;
}
The output is as below.
tool coolbox
1 1 3
It took 0.002992s in inner class
It took 4.13945s in main function
It means 'tool' and 'coolbox' have a substring 'ool'
But I am confused that there is a big difference between two times.
Because the first time is total time and the second time is algorithm running time, I have to think its difference time is the elapsed time for declaration variables.
But it looks weird because I think declaration variables time is short.
Is there a mistake in measuring the elapsed time?
Please give me a hint for troubleshoot. Thank you for reading!
