| 両方とも前のリビジョン前のリビジョン次のリビジョン | 前のリビジョン |
| softwares:nestdaq:cplusplus [2024/01/24 16:25] – [型を調べる] kobayash | softwares:nestdaq:cplusplus [2024/02/02 16:19] (現在) – [std::chrono ライブラリ] kobayash |
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| * 参考: Stack Overflow -- platform-specific std::chrono::high_resolution_clock::period::num https://stackoverflow.com/questions/47687645/platform-specific-stdchronohigh-resolution-clockperiodnum | * 参考: Stack Overflow -- platform-specific std::chrono::high_resolution_clock::period::num https://stackoverflow.com/questions/47687645/platform-specific-stdchronohigh-resolution-clockperiodnum |
| * 参考: Stack Overflow -- Different behaviour of system_clock on windows and linux https://stackoverflow.com/questions/55120594/different-behaviour-of-system-clock-on-windows-and-linux | * 参考: Stack Overflow -- Different behaviour of system_clock on windows and linux https://stackoverflow.com/questions/55120594/different-behaviour-of-system-clock-on-windows-and-linux |
| | === std::chrono ライブラリクロックの違い === |
| | * 以下のようなコードを書く<code> |
| | #include <iostream> |
| | #include <thread> |
| | #include <chrono> |
| |
| | int main(int argc,char *argv[]){ |
| | std::chrono::system_clock::time_point system_clock_start = std::chrono::system_clock::now(); |
| | std::chrono::steady_clock::time_point steady_clock_start = std::chrono::steady_clock::now(); |
| | std::chrono::high_resolution_clock::time_point h_reso_clock_start = std::chrono::high_resolution_clock::now(); |
| | std::chrono::nanoseconds system_clock_start_epoch = std::chrono::duration_cast<std::chrono::nanoseconds> (system_clock_start.time_since_epoch()); |
| | std::chrono::nanoseconds steady_clock_start_epoch = std::chrono::duration_cast<std::chrono::nanoseconds> (steady_clock_start.time_since_epoch()); |
| | std::chrono::nanoseconds h_reso_clock_start_epoch = std::chrono::duration_cast<std::chrono::nanoseconds> (h_reso_clock_start.time_since_epoch()); |
| | |
| | for (int i = 0; i < 100; i++) { |
| | std::chrono::system_clock::time_point system_clock_now = std::chrono::system_clock::now(); |
| | std::chrono::steady_clock::time_point steady_clock_now = std::chrono::steady_clock::now(); |
| | std::chrono::high_resolution_clock::time_point h_reso_clock_now = std::chrono::high_resolution_clock::now(); |
| | std::chrono::nanoseconds system_clock_now_epoch = std::chrono::duration_cast<std::chrono::nanoseconds> (system_clock_now.time_since_epoch()); |
| | std::chrono::nanoseconds steady_clock_now_epoch = std::chrono::duration_cast<std::chrono::nanoseconds> (steady_clock_now.time_since_epoch()); |
| | std::chrono::nanoseconds h_reso_clock_now_epoch = std::chrono::duration_cast<std::chrono::nanoseconds> (h_reso_clock_now.time_since_epoch()); |
| | std::chrono::nanoseconds system_clock_duration = std::chrono::duration_cast<std::chrono::nanoseconds> (system_clock_now - system_clock_start); |
| | std::chrono::nanoseconds steady_clock_duration = std::chrono::duration_cast<std::chrono::nanoseconds> (steady_clock_now - steady_clock_start); |
| | std::chrono::nanoseconds h_reso_clock_duration = std::chrono::duration_cast<std::chrono::nanoseconds> (h_reso_clock_now - h_reso_clock_start); |
| | |
| | |
| | std::time_t now = std::chrono::system_clock::to_time_t(system_clock_now); |
| | std::string s(30, '\0'); |
| | std::strftime(&s[0], s.size(), "%Y-%m-%d %H:%M:%S", std::localtime(&now)); |
| | |
| | std::cout << "system_clock_now: " << s << std::endl; |
| | std::cout << "system_clock_now_epoch.count(): " << system_clock_now_epoch.count() << std::endl; |
| | std::cout << "steady_clock_now_epoch.count(): " << steady_clock_now_epoch.count() << std::endl; |
| | std::cout << "h_reso_clock_now_epoch.count(): " << h_reso_clock_now_epoch.count() << std::endl; |
| | std::cout << "system_clock_duration.count(): " << system_clock_duration.count() << std::endl; |
| | std::cout << "steady_clock_duration.count(): " << steady_clock_duration.count() << std::endl; |
| | std::cout << "h_reso_clock_duration.count(): " << h_reso_clock_duration.count() << std::endl; |
| | std::cout << std::endl; |
| | |
| | std::this_thread::sleep_for(std::chrono::seconds(1)); |
| | } |
| | return 0; |
| | } |
| | </code> |
| | * macOS 12.3.1 でシステムの時計をずらせるように、network の時刻同期を切る。<code> |
| | $ sudo systemsetup -setusingnetworktime off |
| | 2024-02-02 15:09:51.126 systemsetup[23124:12338196] ### Error:-99 File:/AppleInternal/Library/BuildRoots/66382bca-8bca-11ec-aade-6613bcf0e2ee/Library/Caches/com.apple.xbs/Sources/Admin/InternetServices.m Line:379 |
| | setUsingNetworkTime: Off |
| | </code> |
| | * macOS 12.3.1 上でコードを実行する。<code>$ ./std_chrono_comp_clocks |
| | system_clock_now: 2024-02-02 15:56:02 |
| | system_clock_now_epoch.count(): 1706856962044809000 |
| | steady_clock_now_epoch.count(): 3446501139918415 |
| | h_reso_clock_now_epoch.count(): 3446501139918476 |
| | system_clock_duration.count(): 3000 |
| | steady_clock_duration.count(): 2728 |
| | h_reso_clock_duration.count(): 2706 |
| | |
| | system_clock_now: 2024-02-02 15:56:03 |
| | system_clock_now_epoch.count(): 1706856963050483000 |
| | steady_clock_now_epoch.count(): 3446502145634015 |
| | h_reso_clock_now_epoch.count(): 3446502145634132 |
| | system_clock_duration.count(): 1005677000 |
| | steady_clock_duration.count(): 1005718328 |
| | h_reso_clock_duration.count(): 1005718362 |
| | |
| | system_clock_now: 2024-02-02 15:56:04 |
| | system_clock_now_epoch.count(): 1706856964055087000 |
| | steady_clock_now_epoch.count(): 3446503150279622 |
| | h_reso_clock_now_epoch.count(): 3446503150279705 |
| | system_clock_duration.count(): 2010281000 |
| | steady_clock_duration.count(): 2010363935 |
| | h_reso_clock_duration.count(): 2010363935 |
| | </code> |
| | * コードを実行中に、別の端末で、コードの実行開始時間より前の時間にシステムの時刻を変更する。<code> |
| | $ sudo systemsetup -settime 15:56:00 |
| | 2024-02-02 15:56:00.000 systemsetup[24235:12388285] ### Error:-99 File:/AppleInternal/Library/BuildRoots/66382bca-8bca-11ec-aade-6613bcf0e2ee/Library/Caches/com.apple.xbs/Sources/Admin/InternetServices.m Line:379 |
| | Set Time: 15:56:00 |
| | </code> |
| | * その後、テストコードの出力を見ると、system_clock_duration.count()がマイナスの値になるが、steady_cklock と high_resolustion_clockは影響されない。<code> |
| | system_clock_now: 2024-02-02 15:56:01 |
| | system_clock_now_epoch.count(): 1706856961000765000 |
| | steady_clock_now_epoch.count(): 3446504154296655 |
| | h_reso_clock_now_epoch.count(): 3446504154296770 |
| | system_clock_duration.count(): -1044041000 |
| | steady_clock_duration.count(): 3014380968 |
| | h_reso_clock_duration.count(): 3014381000 |
| | |
| | system_clock_now: 2024-02-02 15:56:02 |
| | system_clock_now_epoch.count(): 1706856962003841000 |
| | steady_clock_now_epoch.count(): 3446505157415128 |
| | h_reso_clock_now_epoch.count(): 3446505157415217 |
| | system_clock_duration.count(): -40965000 |
| | steady_clock_duration.count(): 4017499441 |
| | h_reso_clock_duration.count(): 4017499447 |
| | |
| | system_clock_now: 2024-02-02 15:56:03 |
| | system_clock_now_epoch.count(): 1706856963007809000 |
| | steady_clock_now_epoch.count(): 3446506161423906 |
| | h_reso_clock_now_epoch.count(): 3446506161423991 |
| | system_clock_duration.count(): 963003000 |
| | steady_clock_duration.count(): 5021508219 |
| | h_reso_clock_duration.count(): 5021508221 |
| | </code> これをみると、std::chrono::high_resolution_clock は std::chrono::steady_clock の別名のようだ。また、Ubuntu MATE 22.03.3 LTS で実行すると、以下のようになる。<code> |
| | $ ./std_chrono_comp_clocks |
| | system_clock_now: 2024-02-02 16:18:15 |
| | system_clock_now_epoch.count(): 1706858295484039608 |
| | steady_clock_now_epoch.count(): 1109260620490710 |
| | h_reso_clock_now_epoch.count(): 1706858295484039845 |
| | system_clock_duration.count(): 1217 |
| | steady_clock_duration.count(): 958 |
| | h_reso_clock_duration.count(): 945 |
| | |
| | system_clock_now: 2024-02-02 16:18:16 |
| | system_clock_now_epoch.count(): 1706858296484348873 |
| | steady_clock_now_epoch.count(): 1109261620800102 |
| | h_reso_clock_now_epoch.count(): 1706858296484349263 |
| | system_clock_duration.count(): 1000310482 |
| | steady_clock_duration.count(): 1000310350 |
| | h_reso_clock_duration.count(): 1000310363 |
| | |
| | system_clock_now: 2024-02-02 16:18:17 |
| | system_clock_now_epoch.count(): 1706858297484600085 |
| | steady_clock_now_epoch.count(): 1109262621051266 |
| | h_reso_clock_now_epoch.count(): 1706858297484600429 |
| | system_clock_duration.count(): 2000561694 |
| | steady_clock_duration.count(): 2000561514 |
| | h_reso_clock_duration.count(): 2000561529 |
| | ... |
| | </code> これを見ると、std::chrono::high_resolution_clock は std::chrono::system_clock の別名のようだ。 |
| | |
| | |
| | ==== Arrow operator (->) in the function declaration ==== |
| | * nestdaq/plugins/TimeUtil.h と TimeUtil.cxx で以下の書き方を見た。<code> |
| | auto update_date(const std::chrono::system_clock::time_point &s, |
| | const std::chrono::steady_clock::time_point &t) |
| | -> const std::pair<std::chrono::nanoseconds, std::chrono::system_clock::time_point>; |
| | </code> この関数を宣言している部分の 矢印 (->) は、関数の戻り値の型を定義しているようだ。 |
| | * 参考: https://stackoverflow.com/questions/22514855/arrow-operator-in-function-heading |
| | * 参考: https://stackoverflow.com/questions/4113365/what-does-mean-in-c/4113390#4113390 |
