title: Intel Compiler versus GCC
body: <p>When I compile an application with Intel's compiler it is slower than when I compile it with GCC. The Intel compiler's output is more than 2x slower. The application contains several nested loops. Are there any differences between GCC and the Intel compiler that I am missing? Do I need to turn on some other flags to improve the Intel compiler's performance? I expected the Intel compiler to be at least as fast as GCC.</p>
  
  <p>Compiler Versions:</p>
  
  <pre>
   Intel version  12.0.0 20101006 
   GCC   version  4.4.4  20100630
  </pre>
  
  <p>The compiler flags are the same with both compilers:</p>
  
  <pre><code>-O3 -openmp -parallel -mSSE4.2 -Wall -pthread
  </code></pre>