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# Building and installing NumPy

## Binary installers

In most use cases the best way to install NumPy on your system is by using an installable binary package for your operating system.

### Windows

Good solutions for Windows are, The Enthought Python Distribution (EPD) (which provides binary installers for Windows, OS X and Redhat) and Python (x, y). Both of these packages include Python, NumPy and many additional packages.

A lightweight alternative is to download the Python installer from www.python.org and the NumPy installer for your Python version from the Sourceforge download site

The NumPy installer includes binaries for different CPU’s (without SSE instructions, with SSE2 or with SSE3) and installs the correct one automatically. If needed, this can be bypassed from the command line with

    numpy-<1.y.z>-superpack-win32.exe /arch nosse

or ‘sse2’ or ‘sse3’ instead of ‘nosse’.

### Linux

Most of the major distributions provide packages for NumPy, but these can lag behind the most recent NumPy release. Pre-built binary packages for Ubuntu are available on the scipy ppa. Redhat binaries are available in the EPD.

### Mac OS X

A universal binary installer for NumPy is available from the download site. The EPD provides NumPy binaries.

## Building from source

A general overview of building NumPy from source is given here, with detailed instructions for specific platforms given seperately.

### Prerequisites

Building NumPy requires the following software installed:

1. Python 2.4.x, 2.5.x or 2.6.x

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

   On Windows: the official python installer at www.python.org 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.

2. Compilers

   To build any extension modules for Python, you’ll need a C compiler. Various NumPy modules use FORTRAN 77 libraries, so you’ll also need a FORTRAN 77 compiler installed.

   Note that NumPy is developed mainly using GNU compilers. Compilers from other vendors such as Intel, Absoft, Sun, NAG, Compaq, Vast, Porland, Lahey, HP, IBM, Microsoft are only supported in the form of community feedback, and may not work out of the box. GCC 3.x (and later) compilers are recommended.

3. Linear Algebra libraries

   NumPy does not require any external linear algebra libraries to be installed. However, if these are available, NumPy’s setup script can detect them and use them for building. A number of different LAPACK library setups can be used, including optimized LAPACK libraries such as ATLAS, MKL or the Accelerate/vecLib framework on OS X.

### 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. This applies for most other cases where different FORTRAN compilers might have been used.

#### Choosing the fortran compiler

To build with g77:

    python setup.py build --fcompiler=gnu

To build with gfortran:

    python setup.py build --fcompiler=gnu95

For more information see:

    python setup.py build --help-fcompiler

#### 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.

### Disabling ATLAS and other accelerated libraries

Usage of ATLAS and other accelerated libraries in Numpy can be disabled via:

    BLAS=None LAPACK=None ATLAS=None python setup.py build

### Supplying additional compiler flags

Additional compiler flags can be supplied by setting the `OPT`, `FOPT` (for Fortran), and `CC` environment variables.

### Building with ATLAS support

#### Ubuntu 8.10 (Intrepid) and 9.04 (Jaunty)

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

This package is not available on amd64 platforms.

NOTE: Ubuntu changed its default fortran compiler from g77 in Hardy to gfortran in Intrepid. If you are building ATLAS from source and are upgrading from Hardy to Intrepid or later versions, you should rebuild everything from scratch, including lapack.

#### 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

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