123 lines
8.5 KiB
HTML
123 lines
8.5 KiB
HTML
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<title>std::chrono::high_resolution_clock</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_chrono_high_resolution_clock skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::</span>high_resolution_clock</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-chrono.html">chrono</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-chrono.html"><chrono></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">class</span> high_resolution_clock<span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<p>类 <code>std::chrono::high_resolution_clock</code> 表示实现提供的拥有最小计次周期的时钟。它可以是 <span class="t-lc"><a href="cpp-chrono-system_clock.html">std::chrono::system_clock</a></span> 或 <span class="t-lc"><a href="cpp-chrono-steady_clock.html">std::chrono::steady_clock</a></span> 的别名，或第三个独立时钟。</p>
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<p><code>std::chrono::high_resolution_clock</code> 满足<a href="cpp-named_req-TrivialClock.html"><span style="font-style:italic">平凡时钟</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(TrivialClock)</span></a> 的要求。</p>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
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<td>成员类型</td>
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<td>定义</td>
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<td><code>rep</code></td>
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<td>表示时钟的时期中计次数的算术类型</td>
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<td><code>period</code></td>
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<td>表示时钟计次周期的 <span class="t-lc"><a href="cpp-numeric-ratio-ratio.html">std::ratio</a></span> 类型，单位为秒</td>
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<td><code>duration</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1"><</span>rep, period<span class="sy1">></span></span></span></td>
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<td><code>time_point</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">high_resolution_clock</span><span class="sy1">></span></span></span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.B8.B8.E9.87.8F">成员常量</span></h3>
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<div><span class="t-lines"><span><span class="t-dsc-small">constexpr bool</span> is_steady</span></span></div>
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<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
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<td>若时间间隔计次始终为常量，即纵使在外部时钟调整的情况下，调用 <a href="cpp-chrono-high_resolution_clock-now.html"><tt>now()</tt></a> 的返回值亦单调递增，则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> ，否则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span><br />
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<span class="t-mark">(公开静态成员常量)</span></td>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<div><a href="cpp-chrono-high_resolution_clock-now.html"><span class="t-lines"><span>now</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
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<td>返回表示时钟当前值的 <span class="t-lc"><a href="cpp-chrono-time_point.html">std::chrono::time_point</a></span><br />
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<span class="t-mark">(公开静态成员函数)</span></td>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p><code>high_resolution_clock</code> 在不同标准库实现之间实现并不一致，尽量不要使用。通常它只是 <span class="t-lc"><a href="cpp-chrono-steady_clock.html">std::chrono::steady_clock</a></span> 或 <span class="t-lc"><a href="cpp-chrono-system_clock.html">std::chrono::system_clock</a></span> 的别名——它是 <code>system_clock</code> 时不是单调的（即时间能后退），但具体实现取决于库或配置。例如：对于 gcc 的 libstdc++ 它是 <code>system_clock</code> ，对于 MSVC 它是 <code>steady_clock</code> ，而对于 clang 的 libc++ 它取决于配置。</p>
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<p>通常用户应该直接使用 <span class="t-lc"><a href="cpp-chrono-steady_clock.html">std::chrono::steady_clock</a></span> 或 <span class="t-lc"><a href="cpp-chrono-system_clock.html">std::chrono::system_clock</a></span> 代替 <code>std::chrono::high_resolution_clock</code> ：对时长度量使用 <code>steady_clock</code> ，对壁钟时间使用 <code>system_clock</code> 。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<div><a href="cpp-chrono-system_clock.html"><span class="t-lines"><span>system_clock</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>来自系统范围实时时钟的壁钟时间<br />
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<span class="t-mark">(类)</span></td>
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<div><a href="cpp-chrono-steady_clock.html"><span class="t-lines"><span>steady_clock</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>决不调整的单调时钟<br />
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<span class="t-mark">(类)</span></td>
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