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Building and installing NumPy
+++++++++++++++++++++++++++++

:Authors: Numpy Developers <numpy-discussion@scipy.org>
:Discussions to: numpy-discussion@scipy.org

.. Contents::

PREREQUISITES
=============

Building NumPy requires the following software installed:

1) Python__ 2.4.x or newer

   On Debian and derivative (Ubuntu): python python-dev

   On Windows: the official python installer on Python__ is enough

   Make sure that the Python package distutils is installed before
   continuing. For example, in Debian GNU/Linux, distutils is included
   in the python-dev package.

   Python must also be compiled with the zlib module enabled.

__ http://www.python.org

Fortran ABI mismatch
====================

The two most popular open source fortran compilers are g77 and gfortran.
Unfortunately, they are not ABI compatible, which means that concretely you
should avoid mixing libraries built with one with another. In particular, if
your blas/lapack/atlas is built with g77, you *must* use g77 when building
numpy and scipy; on the contrary, if your atlas is built with gfortran, you
*must* build numpy/scipy with gfortran.

Choosing the fortran compiler
-----------------------------

To build with g77:

    python setup.py build --fcompiler=gnu

To build with gfortran:

    python setup.py build --fcompiler=gnu95

How to check the ABI of blas/lapack/atlas
-----------------------------------------

One relatively simple and reliable way to check for the compiler used to build
a library is to use ldd on the library. If libg2c.so is a dependency, this
means that g77 has been used. If libgfortran.so is a a dependency, gfortran has
been used. If both are dependencies, this means both have been used, which is
almost always a very bad idea.

Building with ATLAS support
===========================

Ubuntu 8.10 (Intrepid)
----------------------

You can install the necessary packages for optimized ATLAS with this command:

    sudo apt-get install libatlas-base-dev

If you have a recent CPU with SIMD suppport (SSE, SSE2, etc...), you should
also install the corresponding package for optimal performances. For example,
for SSE2:

    sudo apt-get install libatlas3gf-sse2

*NOTE*: if you build your own atlas, Intrepid changed its default fortran
compiler to gfortran. So you should rebuild everything from scratch, including
lapack, to use it on Intrepid.

Ubuntu 8.04 and lower
---------------------

You can install the necessary packages for optimized ATLAS with this command:

    sudo apt-get install atlas3-base-dev

If you have a recent CPU with SIMD suppport (SSE, SSE2, etc...), you should
also install the corresponding package for optimal performances. For example,
for SSE2:

    sudo apt-get install atlas3-sse2