FAQ Database Discussion Community

Cast chrono::milliseconds to uint64_t?

Assuming I have the number of milliseconds in variable x: chrono::milliseconds x = std::chrono::duration_cast<chrono::milliseconds>(something); how do I convert x from chrono::milliseconds to uint64_t? I have tried: uint64_t num = std::chrono::duration_cast<uint64_t>(x); but it says: no matching function for call to duration_cast(std::chrono::milliseconds&) ...

How to run a clock on its own thread

I'm trying to create a step sequencer in C++ that will eventually send out MIDI data. I created it by having a clock on its own thread that calculates the amount of time since the last beat, and if it is time for the next beat, it writes a piece...

timing a function call as if-statement condition in cpp

I have a function and sometimes it gets called as a condition in if-statements, and I am interested to time exactly these calls. I wonder if there is any way to do something like this for timing it in cpp: using watch = std::chrono::high_resolution_clock; std::chrono::nanoseconds time(0); if ( auto start...

Avoiding CPU Contention

I have a program that I want to calculate its time of execution : #include <iostream> #include <boost/chrono.hpp> using namespace std; int main(int argc, char* const argv[]) { boost::chrono::system_clock::time_point start = boost::chrono::system_clock::now(); // Intructions to burn time boost::chrono::duration<double> sec = boost::chrono::system_clock::now() - start; cout <<"---- time execution is " <<...

Convert double to time_t

I have a double containing seconds. I would like to convert this into a time_t. I can't find a standard function which accomplishes this. Do I have to fill out the time_t by hand?...

C++ condition variable wait_for not behaving as expected

I am having a problem understanding why a test case that I think should be passing is failing most of the time. I have distilled the test down to the condition variable and using the wait_for method, specifically testing it to see if it does indeed wait for at least...

Is There an Upper Bound in my locale for Time Related Information?

Is there a definition somewhere in the standard namespace that sets forward: Months in a year Days in a week Hours in a day Minutes in an hour Seconds in a minute The struct tm has contains member variables that must be in these ranges, but I can't find the...

C++ chrono library on Raspberry Pi

On a Raspberry Pi 2, I need to call a php file on a regular basis, typically every 100ms. I found this c++ code which looks like it does what I need and a test version of it compiles and runs fine using CodeBlock on Windows. I've updated the wheezy...

Running a function for specified duration : C++ with

I need to implement a function that should do specified task for specified duration which is passed to it as parameter (std::chrono::milliseconds). I have come up with code : void Run(std::chrono::milliseconds ms) { std::chrono::time_point<std::chrono::system_clock> start, end; start = std::chrono::system_clock::now(); std::chrono::duration<double> elapsed_seconds = end - start; while (elapsed_seconds <= (ms /...

How to use `duration_cast` for a derived class?

I'm cleaning up my timer class using std::chrono. Everything else went smooth except that I cannot seem to apply duration_cast to derived classes. Well, I made it work in a different way, but I'd still like to know what I missed. See here for the error message. #include <iostream> #include...

Is there a way to assign zero to std::chrono::nanoseconds

Is there a way to assign zero to a duration of type std::chrono::nanoseconds? I tried duration::zero but it failed.

Why does coliru return the same values for chrono::system_clock::now().time_since_epoch()?

While testing someone else's code on coliru, I noticed that std::chrono::system_clock::now().time_since_epoch() returns the same values on multiple runs. I tested the following code with g++ and clang++ on coliru. #include <iostream> #include <chrono> int main() { auto seed = std::chrono::system_clock::now().time_since_epoch().count(); std::cout << seed << "\n"; std::cout << std::chrono::system_clock::now().time_since_epoch().count() << "\n";...

std thread sleep_for doesnt work with some chrono::duration

I am using VS2012 and I have problem with following example: #include <chrono> #include <thread> int main() { // doesn't compile and I don't understand why: std::this_thread::sleep_for(std::chrono::duration<double>(0.1)); // I can use this but still I would like to know the reason: std::this_thread::sleep_for(std::chrono::duration<long long, std::milli>(100)); return 0; } Both duration should...

DateTime to UTC

What is the proper way to convert date time values to UTC in milliseconds? I've been looking into std::chrono and boost without really finding a pragmatic way to accomplish this, any ideas? i.e. auto local_time_to_utc_milliseconds(int year, int month, int day, int hour, int minute, int second, int millisecond) -> std::uint64_t...

Is it possible to restrict a member function from accessing a member variable?

I have a thread class similar to this: class thr { void run() { for (;;) { // block on a queue // do some processing ++loops_; } } void get_metrics(int& qps) { std::chrono::steady_clock::time_point now = std::chrono::steady_clock::now(); double delta = std::chrono::duration<double>(now - last_metrics_time_).count(); qps = std::round(loops_ / delta); loops_ =...

C++ chrono epoch is 100000 times smaller?

THe code below returns number like 14517044: typedef std::chrono::high_resolution_clock Clock; typedef std::chrono::milliseconds Milliseconds; unsigned long res = std::chrono::duration_cast<Milliseconds>(Clock::now().time_since_epoch()).count(); printf("epoch %lu", res); But http://www.epochconverter.com/ site shows numbers like 1426143327, where as it is in seconds. So the epoch with Milliseconds has 8 digits and epoch with seconds has 10 digits? What...

Can't verify the conversion from time_point to tm and tm back to time_point

I created a current time_point and converted it to structure tm and printed it's values. Now converted this tm structure to time_point. On comparing the first and second time_points, it is telling that they're different. But the values of structure are exactly same. Can someone spot, where I'm doing wrong?...

Convert chrono duration to time_point

How can I convert a chrono duration to a time_point, which is later than clock's epoch with the given duration? I tried to find epoch time in chrono clock without success.