# 3. Installing the software¶

## 3.1. Hardware requirements¶

PSFEx runs in (ANSI) text-mode from a shell. A window system is not necessary for basic operation.

When it comes to memory usage, the amount required by PSFEx depends mostly on the number of point sources present in the input catalogues times the number of pixels in the small image that represents each of them. A typical figure is about 15 kbytes per point source; hence even on a modest computer with 1GB of memory, more than 20,000 point sources can easily be accommodated at once.

Note that PSFEx takes advantage of multiple CPU cores for some operations.

## 3.2. Obtaining PSFEx¶

For Linux users, the simplest way to have PSFEx up and running is to install the standard binary package the comes with your Linux distribution. Run, e.g., apt-get psfex (on Debian) or dnf psfex (Fedora) and PSFEx, as well as all its dependencies, will automatically be installed. If you decided to install the package this way you may skip the following and move straight to the next section.

However if PSFEx is not available in your distribution, or to obtain the most recent version, the PSFEx source package can be downloaded from the official GitHub repository . One may choose one of the stable releases, or for the fearless, a copy of the current master development branch.

## 3.3. Software requirements¶

PSFEx has been developed on GNU/Linux machines and should compile on any POSIX-compliant system (this includes Apple OS X® and Cygwin on Microsoft Windows®, at the price of some difficulties with the configuration), provided that the development packages of the following libraries have been installed:

On Fedora/Redhat distributions for instance, the development packages above are available as atlas-devel, fftw-devel and plplot-devel. PLPlot is only required for producing diagnostic plots. Note that ATLAS and FFTw are not necessary if PSFEx is linked with Intel®‘s MKL library.

## 3.4. Installation¶

To install from the GitHub source package, you must first uncompress the archive:

$unzip psfex-<version>.zip  A new directory called psfex-<version> should now appear at the current location on your disk. Enter the directory and generate the files required by the autotools, which the package relies on: $ cd psfex-<version>
$sh autogen.sh  A configure script is created. This script has many options, which may be listed with the --help option: $ ./configure --help


No options are required for compiling with the default GNU C compiler (gcc) if all the required libraries are installed at their default locations:

$./configure  Compared to gcc and the librairies above, the combination of the Intel® compiler (icc) and the MKL libraries can give the PSFEx executable a strong boost in performance, thanks to better vectorized code. If icc and the MKL are installed on your system [4] , you can take advantage of them using $ ./configure --enable-mkl


Additionally, if the PSFEx binary is to be run on a different machine that does not have icc and the MKL installed (e.g., a cluster computing node), you must configure a partially statically linked executable using

$./configure --enable-mkl --enable-auto-flags --enable-best-link  In all cases, PSFEx can now be compiled with $ make -j


An src/psfex executable is created. For system-wide installation, run the usual

$sudo make install  You may now check that the software is properly installed by simply typing in your shell: $ psfex


which will return the version number and other basic information (note that some shells require the rehash command to be run before making a freshly installed executable accessible in the execution path).

 [1] Mac OS X .dmg packages should be available soon.
 [2] Use the --with-atlas and/or --with-atlas-incdir options of the PSFEx configure script to specify the ATLAS library and include paths if ATLAS files are installed at unusual locations.
 [3] Make sure that FFTw has been compiled with configure options --enable-threads --enable-float.
 [4] The Linux versions of the Intel® compiler and MKL are available for free to academic researchers, students, educators and open source contributors.