final/test/thread/thread.threads/thread.thread.this/sleep_for.pass.cpp

//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// <thread>

// template <class Rep, class Period>
//   void sleep_for(const chrono::duration<Rep, Period>& rel_time);

#include <thread>
#include <cstdlib>
#include <cassert>

int main()
{
    typedef std::chrono::system_clock Clock;
    typedef Clock::time_point time_point;
    typedef Clock::duration duration;
    std::chrono::milliseconds ms(500);
    time_point t0 = Clock::now();
    std::this_thread::sleep_for(ms);
    time_point t1 = Clock::now();
    std::chrono::nanoseconds ns = (t1 - t0) - ms;
    std::chrono::nanoseconds err = 5 * ms / 100;
    // The time slept is within 5% of 500ms
    assert(std::abs(ns.count()) < err.count());
}