title: How can the C++ Eigen library perform better than specialized vendor libraries?
body: <p>I was looking over the performance benchmarks: <a href="http://eigen.tuxfamily.org/index.php?title=Benchmark" rel="noreferrer">http://eigen.tuxfamily.org/index.php?title=Benchmark</a></p>
  
  <p>I could not help but notice that eigen appears to consistently outperform all the specialized vendor libraries.  The questions is: how is it possible?  One would assume that mkl/goto would use processor specific tuned code, while eigen is rather generic.</p>
  
  <p>Notice this <a href="http://download.tuxfamily.org/eigen/btl-results-110323/aat.pdf" rel="noreferrer">http://download.tuxfamily.org/eigen/btl-results-110323/aat.pdf</a>, essentially a dgemm.  For N=1000 Eigen gets roughly 17Gf, MKL only 12Gf</p>