title: Link ATLAS/MKL to an installed Numpy
body: <p><strong>TL;DR</strong> how to link ATLAS/MKL to existing Numpy without rebuilding.</p>
  
  <p>I have used Numpy to calculate with the large matrix and I found that it is very slow because Numpy only use 1 core to do calculation. After doing a lot of search I figure that my Numpy does not link to some optimized library like ATLAS/MKL. Here is my config of numpy:</p>
  
  <pre><code>&gt;&gt;&gt;import numpy as np
  &gt;&gt;&gt;np.__config__.show()
  blas_info:
      libraries = ['blas']
      library_dirs = ['/usr/lib']
      language = f77
  lapack_info:
      libraries = ['lapack']
      library_dirs = ['/usr/lib']
      language = f77
  atlas_threads_info:
      NOT AVAILABLE
  blas_opt_info:
      libraries = ['blas']
      library_dirs = ['/usr/lib']
      language = f77
      define_macros = [('NO_ATLAS_INFO', 1)]
  atlas_blas_threads_info:
    NOT AVAILABLE
  openblas_info:
    NOT AVAILABLE
  lapack_opt_info:
      libraries = ['lapack', 'blas']
      library_dirs = ['/usr/lib']
      language = f77
      define_macros = [('NO_ATLAS_INFO', 1)]
  atlas_info:
    NOT AVAILABLE
  lapack_mkl_info:
    NOT AVAILABLE
  blas_mkl_info:
    NOT AVAILABLE
  atlas_blas_info:
    NOT AVAILABLE
  mkl_info:
    NOT AVAILABLE
  </code></pre>
  
  <p>For this reason, I want to link ATLAS/MKL to Numpy. However, my Numpy is installed from PIP so I don't want to install manually because I want to use the latest version. I have done some search but they are only for building from scratch. For this reason, my question are:</p>
  
  <ul>
  <li>Are there any way to link ATLAS/MKL to Numpy without rebuilding again?</li>
  <li>I have found that the config info is saved in <strong>_<em>config</em>_.py</strong> in the installed folder of Numpy. So will modifying it solve my problem? If yes, would you please show me how?</li>
  </ul>