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POPerformance of qsort vs std::sort?
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  1. POPerformance of qsort vs std::sort?
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    copied!<p>According Scott Meyers, in his Effective STL book - item 46. He claimed that <a href="http://en.cppreference.com/w/cpp/algorithm/sort" rel="noreferrer"><code>std::sort</code></a> is about 670% faster than <a href="http://en.cppreference.com/w/cpp/algorithm/qsort" rel="noreferrer"><code>std::qsort</code></a> due to the fact of inline. I tested myself, and I saw that qsort is faster :( ! Could anyone help me to explain this strange behavior? </p> <pre><code>#include &lt;iostream&gt; #include &lt;vector&gt; #include &lt;algorithm&gt; #include &lt;cstdlib&gt; #include &lt;ctime&gt; #include &lt;cstdio&gt; const size_t LARGE_SIZE = 100000; struct rnd { int operator()() { return rand() % LARGE_SIZE; } }; int comp( const void* a, const void* b ) { return ( *( int* )a - *( int* )b ); } int main() { int ary[LARGE_SIZE]; int ary_copy[LARGE_SIZE]; // generate random data std::generate( ary, ary + LARGE_SIZE, rnd() ); std::copy( ary, ary + LARGE_SIZE, ary_copy ); // get time std::time_t start = std::clock(); // perform quick sort C using function pointer std::qsort( ary, LARGE_SIZE, sizeof( int ), comp ); std::cout &lt;&lt; "C quick-sort time elapsed: " &lt;&lt; static_cast&lt;double&gt;( clock() - start ) / CLOCKS_PER_SEC &lt;&lt; "\n"; // get time again start = std::clock(); // perform quick sort C++ using function object std::sort( ary_copy, ary_copy + LARGE_SIZE ); std::cout &lt;&lt; "C++ quick-sort time elapsed: " &lt;&lt; static_cast&lt;double&gt;( clock() - start ) / CLOCKS_PER_SEC &lt;&lt; "\n"; } </code></pre> <p>This is my result:</p> <pre><code>C quick-sort time elapsed: 0.061 C++ quick-sort time elapsed: 0.086 Press any key to continue . . . </code></pre> <p><strong>Update</strong></p> <p>Effective STL 3rd Edition ( 2001 )<br> Chapter 7 Programming with STL<br> Item 46: Consider function objects instead of functions as algorithm parameters. </p> <p>Best regards, </p>
 

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