|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Member functions | ||||
utc_clock::now | ||||
| Time point I/O | ||||
| Leap second insertion information | ||||
staticstd::chrono::time_point<std::chrono::utc_clock> now(); | (since C++20) | |
Returns a time point representing the current point in time.The result is calculated as if bystd::chrono::utc_clock::from_sys(std::chrono::system_clock::now()). Implementations may use a more accurate value of UTC time.
A time point representing the current time.
#include <chrono>#include <cstddef>#include <iomanip>#include <iostream>#include <numeric>#include <vector> volatileint sink;// prevents optimization void do_some_work(std::size_t size){std::vector<int> v(size,42); sink=std::accumulate(v.begin(), v.end(),0);// ensures side effect} int main(){std::cout<<std::fixed<<std::setprecision(9)<<std::left;for(auto size{1ull}; size<1000'000'000ull; size*=100){constauto start= std::chrono::utc_clock::now(); do_some_work(size);constauto end= std::chrono::utc_clock::now();conststd::chrono::duration<double> diff= end- start;std::cout<<"start = "<< start<<"; end = "<< end<<";\n";std::cout<<"diff = "<< diff<<"; size = "<< size<<'\n';}}
Possible output:
start = 2024-10-25 13:37:42.016233947; end = 2024-10-25 13:37:42.016239362;diff = 0.000005415s; size = 1start = 2024-10-25 13:37:42.016384595; end = 2024-10-25 13:37:42.016386581;diff = 0.000001986s; size = 100start = 2024-10-25 13:37:42.016394197; end = 2024-10-25 13:37:42.016445830;diff = 0.000051633s; size = 10000start = 2024-10-25 13:37:42.016452737; end = 2024-10-25 13:37:42.022496657;diff = 0.006043920s; size = 1000000start = 2024-10-25 13:37:42.022511298; end = 2024-10-25 13:37:42.658639946;diff = 0.636128648s; size = 100000000
