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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::steady_clock::</span>now</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-chrono.html">chrono</a>&lrm; | <a href="cpp-chrono-steady_clock.html">steady clock</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">static</span> <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">&lt;</span><a href="cpp-chrono-steady_clock.html"><span class="kw1006">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">steady_clock</span></span></a><span class="sy1">&gt;</span> now<span class="br0">(</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
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<p>&#36820;&#22238;&#34920;&#31034;&#24403;&#21069;&#26102;&#38388;&#30340;&#26102;&#38388;&#28857;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<p>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#34920;&#31034;&#24403;&#21069;&#26102;&#38388;&#30340;&#26102;&#38388;&#28857;&#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;vector&gt;</span>
<span class="co2">#include &lt;numeric&gt;</span>
<span class="co2">#include &lt;chrono&gt;</span>
<span class="kw4">volatile</span> <span class="kw4">int</span> sink<span class="sy4">;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">auto</span> size <span class="sy1">=</span> 1ull<span class="sy4">;</span> size <span class="sy1">&lt;</span> 1000000000ull<span class="sy4">;</span> size <span class="sy2">*</span><span class="sy1">=</span> <span class="nu0">100</span><span class="br0">)</span> <span class="br0">{</span>
<span class="co1">// &#35760;&#24405;&#24320;&#22987;&#26102;&#38388;</span>
<span class="kw4">auto</span> start <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">steady_clock</span><span class="sy4">::</span><span class="me2">now</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// &#20570;&#19968;&#20123;&#24037;&#20316;</span>
<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> v<span class="br0">(</span>size, <span class="nu0">42</span><span class="br0">)</span><span class="sy4">;</span>
sink <span class="sy1">=</span> <a href="cpp-algorithm-accumulate.html"><span class="kw1651">std::<span class="me2">accumulate</span></span></a><span class="br0">(</span>v.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, v.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>, 0u<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// &#30830;&#20445;&#20854;&#21103;&#25928;&#24212;</span>
<span class="co1">// &#35760;&#24405;&#32467;&#26463;&#26102;&#38388;</span>
<span class="kw4">auto</span> end <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">steady_clock</span><span class="sy4">::</span><span class="me2">now</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<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">&lt;</span><span class="kw4">double</span><span class="sy1">&gt;</span> diff <span class="sy1">=</span> end<span class="sy2">-</span>start<span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;Time to fill and iterate a vector of &quot;</span>
<span class="sy1">&lt;&lt;</span> size <span class="sy1">&lt;&lt;</span> <span class="st0">&quot; ints : &quot;</span> <span class="sy1">&lt;&lt;</span> diff.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot; s<span class="es1">\n</span>&quot;</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="br0">}</span></pre></div>
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<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
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<pre class="de1">Time to fill and iterate a vector of 1 ints : 2.43e-07 s
Time to fill and iterate a vector of 100 ints : 4.1e-07 s
Time to fill and iterate a vector of 10000 ints : 2.519e-05 s
Time to fill and iterate a vector of 1000000 ints : 0.00207669 s
Time to fill and iterate a vector of 100000000 ints : 0.423087 s</pre></div>
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