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POVarying performance of MSVC release exe
 

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  1. POVarying performance of MSVC release exe
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    <p>I am curious what could be the reason for highly varying performance of the same executable. Sometimes, I run it and it takes 20 seconds and sometimes it is 110. Source is compiled with MSVC in Release mode with standard options.</p> <p>The code is here:</p> <pre><code>vector&lt;double&gt; Un; vector&lt;double&gt; Ucur; double *pUn, *pUcur; ... // time marching for (old_time=time-logfreq, time+=dt; time &lt;= end_time; time+=dt) { for (i=1, j=Un.size()-1, pUn=&amp;Un[1], pUcur=&amp;Ucur[1]; i &lt; j; ++i, ++pUn, ++pUcur) { *pUcur = (*pUn)*(1.0-0.5*alpha*( *(pUn+1) - *(pUn-1) )); } Ucur[0] = (Un[0])*(1.0-0.5*alpha*( Un[1] - Un[j] )); Ucur[j] = (Un[j])*(1.0-0.5*alpha*( Un[0] - Un[j-1] )); Un = Ucur; } </code></pre> <p><strong>EDIT</strong></p> <p>Sorry not to mention input data. The vectors Un and Ucur are initialized to 2000 elements with value 0. No data is read/written. No interaction with console. When I say sometimes I run it means that I have console open, no other applications running , processor throttling disabled. I keep executing application after it finishes. I guess it has to do with caching or something like that but I am not good on low-level things.</p> <p><strong>UPDATE</strong></p> <p>Issue was resolved when I switched the arguments in this function from addresses to variables. Before I had <code>double &amp;time, double &amp;dt, double &amp;end_time</code><br> Now: <code>double time, double dt, double end_time</code></p> <p>It appears to be memory-related issue... Hope, it helps anybody</p>
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