title: Matlab eigs fail with large matrix
body: <p>In matlab, I use function 'eigs()' to get a few (about 10) of the smallest eigen vectors of a large matrix (5000x5000). Like this:</p>
  
  <pre><code>[V,UU] = eigs(A, 10,'sm');
  </code></pre>
  
  <p>After some trying, I found that the largest size of matrix 'eigs()' is able to deal with is something between 1300 and 1500. </p>
  
  <p>With bigger matrices, it pops up error message like '(A-sigma*I)is singular. The shift is an eigenvalue.' or something about 'APPAPK'(when using 'sr') in the Command Window.</p>
  
  <p>I got some info about these errors from google, but they are about some inner code or theorem(sounds like one) which I don't quite understand.</p>
  
  <p>So, I want to know if there are any tricks with eigs to make it work with large matrix? </p>
  
  <p>Thanks for your time and help.</p>