# Installation¶

## Dependencies¶

galpy requires the numpy, scipy, and matplotlib packages; these must be installed or the code will not be able to be imported.

Optional dependencies are: astropy for Quantity support (used throughout galpy when installed), astroquery for the Orbit.from_name initialization method (to initialize using a celestial object’s name), numexpr for plotting arbitrary expressions of Orbit quantities, and pynbody for use of SnapshotRZPotential and InterpSnapshotRZPotential.

To be able to use the fast C extensions for orbit integration and action-angle calculations, the GNU Scientific Library (GSL) needs to be installed (see below).

## With conda¶

The easiest way to install the latest released version of galpy is using conda:

conda install galpy -c conda-forge


or:

conda config --add channels conda-forge
conda install galpy


Installing with conda will automatically install the required dependencies (numpy, scipy, and matplotlib) and the GSL, but not the optional dependencies.

## With pip¶

galpy can also be installed using pip. Some advanced features require the GNU Scientific Library (GSL; see below). If you want to use these, install the GSL first (or install it later and re-install using the upgrade command above). Then do:

pip install galpy


pip install -U --no-deps galpy


Installing with pip will automatically install the required dependencies (numpy, scipy, and matplotlib), but not the optional dependencies or the GSL (which needs to be installed before the pip installation of galpy).

The latest updates in galpy can be installed using:

pip install -U --no-deps git+git://github.com/jobovy/galpy.git#egg=galpy


or:

pip install -U --no-deps --install-option="--prefix=~/local" git+git://github.com/jobovy/galpy.git#egg=galpy


for a local installation. The latest updates can also be installed from the source code downloaded from github using the standard python setup.py installation:

python setup.py install


or:

python setup.py install --prefix=~/local


for a local installation.

## Installing from a branch¶

If you want to use a feature that is currently only available in a branch, do:

pip install -U --no-deps git+git://github.com/jobovy/galpy.git@dev#egg=galpy


to, for example, install the dev branch.

## Installing from source on Windows¶

Versions >1.3 should be able to be compiled on Windows systems using the Microsoft Visual Studio C compiler (>= 2015). For this you need to first install the GNU Scientific Library (GSL), for example using Anaconda (see below). Similar to on a UNIX system, you need to set paths to the header and library files where the GSL is located. On Windows, using the CDM commandline, this is done as:

set INCLUDE=%CONDA_PREFIX%\Library\include;%INCLUDE%
set LIB=%CONDA_PREFIX%\Library\lib;%LIB%
set LIBPATH=%CONDA_PREFIX%\Library\lib;%LIBPATH%


If you are using the Windows PowerShell (which newer versions of the Anaconda prompt might set as the default), do:

$env:INCLUDE="$env:CONDA_PREFIX\Library\include"
$env:LIB="$env:CONDA_PREFIX\Library\lib"
$env:LIBPATH="$env:CONDA_PREFIX\Library\lib"


where in this example CONDA_PREFIX is the path of your current conda environment (the path that ends in \ENV_NAME). If you have installed the GSL somewhere else, adjust these paths (but do not use YOUR_PATH\include\gsl or YOUR_PATH\lib\gsl as the paths, simply use YOUR_PATH\include and YOUR_PATH\lib).

To compile with OpenMP on Windows, you have to install Intel OpenMP via:

conda install -c anaconda intel-openmp


and then to compile the code:

python setup.py install


If you encounter any issue related to OpenMP during compilation, you can do:

python setup.py install --no-openmp


## Installing from source with Intel Compiler¶

Compiling galpy with an Intel Compiler can give significant performance improvements on 64-bit Intel CPUs. Moreover students can obtain a free copy of an Intel Compiler at this link.

To compile the galpy C extensions with the Intel Compiler on 64bit MaxOS/Linux do:

python setup.py build_ext --inplace --compiler=intelem


and to compile the galpy C extensions with the Intel Compiler on 64bit Windows do:

python setup.py build_ext --inplace --compiler=intel64w


Then you can simply install with:

python setup.py install


or other similar installation commands, or you can build your own wheels with:

python setup.py sdist bdist_wheel


## Installing the TorusMapper code¶

Since v1.2, galpy contains a basic interface to the TorusMapper code of Binney & McMillan (2016). This interface uses a stripped-down version of the TorusMapper code, that is not bundled with the galpy code, but kept in a fork of the original TorusMapper code. Installation of the TorusMapper interface is therefore only possible when installing from source after downloading or cloning the galpy code and using the python setup.py install method above.

To install the TorusMapper code, before running the installation of galpy, navigate to the top-level galpy directory (which contains the setup.py file) and do:

git clone https://github.com/jobovy/Torus.git galpy/actionAngle/actionAngleTorus_c_ext/torus
cd galpy/actionAngle/actionAngleTorus_c_ext/torus
git checkout galpy
cd -


Then proceed to install galpy using the python setup.py install technique or its variants as usual.

## Installation FAQ¶

### What is the required numpy version?¶

galpy should mostly work for any relatively recent version of numpy, but some advanced features, including calculating the normalization of certain distribution functions using Gauss-Legendre integration require numpy version 1.7.0 or higher.

### I get warnings like “galpyWarning: integrateFullOrbit_c extension module not loaded, because galpy_integrate_c.so image was not found”¶

This typically means that the GNU Scientific Library (GSL) was unavailable during galpy’s installation, causing the C extensions not to be compiled. Most of the galpy code will still run, but slower because it will run in pure Python. The code requires GSL versions >= 1.14. If you believe that the correct GSL version is installed for galpy, check that the library can be found during installation (see below).

### I get the warning “galpyWarning: actionAngleTorus_c extension module not loaded, because galpy_actionAngleTorus_c.so image was not found”¶

This is typically because the TorusMapper code was not compiled, because it was unavailable during installation. This code is only necessary if you want to use galpy.actionAngle.actionAngleTorus. See above for instructions on how to install the TorusMapper code.

### How do I install the GSL?¶

Certain advanced features require the GNU Scientific Library (GSL), with action calculations requiring version 1.14 or higher. The easiest way to install this is using its Anaconda build:

conda install -c conda-forge gsl


If you do not want to go that route, on a Mac, the next easiest way to install the GSL is using Homebrew as:

brew install gsl --universal


You should be able to check your version using (on Mac/Linux):

gsl-config --version


On Linux distributions with apt-get, the GSL can be installed using:

apt-get install libgsl0-dev


### The galpy installation fails because of C compilation errors¶

galpy’s installation can fail due to compilation errors, which look like:

error: command 'gcc' failed with exit status 1


or:

error: command 'clang' failed with exit status 1


or:

error: command 'cc' failed with exit status 1


This is typically because the compiler cannot locate the GSL header files or the GSL library. You can tell the installation about where you’ve installed the GSL library by defining (for example, when the GSL was installed under /usr; the LD_LIBRARY_PATH part of this may or may not be necessary depending on your system):

export CFLAGS=-I/usr/include
export LDFLAGS=-L/usr/lib
export LD_LIBRARY_PATH=-L/usr/lib


or:

setenv CFLAGS -I/usr/include
setenv LDFLAGS -L/usr/lib
setenv LD_LIBRARY_PATH -L/usr/lib


depending on your shell type (change the actual path to the include and lib directories that have the gsl directory). If you already have CFLAGS, LDFLAGS, and LD_LIBRARY_PATH defined you just have to add the '-I/usr/include' and '-L/usr/lib' to them.

If you are on a Mac or UNIX system (e.g., Linux), you can find the correct CFLAGS and LDFLAGS/LD_LIBRARY_path entries by doing:

gsl-config --cflags
gsl-config --libs


(don’t include the -lgsl lgslcblas portion of the latter output.)

### I have defined CFLAGS, LDFLAGS, and LD_LIBRARY_PATH, but the compiler does not seem to include these and still returns with errors¶

This typically happens if you install using sudo, but have defined the CFLAGS etc. environment variables without using sudo. Try using sudo -E instead, which propagates your own environment variables to the sudo user.

### I’m having issues with OpenMP¶

galpy uses OpenMP to parallelize various of the computations done in C. galpy can be installed without OpenMP by specifying the option --no-openmp when running the python setup.py commands above:

python setup.py install --no-openmp


or when using pip as follows:

pip install -U --no-deps --install-option="--no-openmp" git+git://github.com/jobovy/galpy.git#egg=galpy


or:

pip install -U --no-deps --install-option="--prefix=~/local" --install-option="--no-openmp" git+git://github.com/jobovy/galpy.git#egg=galpy


for a local installation. This might be useful if one is using the clang compiler, which is the new default on macs with OS X (>= 10.8), but does not support OpenMP. clang might lead to errors in the installation of galpy such as:

ld: library not found for -lgomp

clang: error: linker command failed with exit code 1 (use -v to see invocation)


If you get these errors, you can use the commands given above to install without OpenMP, or specify to use gcc by specifying the CC and LDSHARED environment variables to use gcc. Note that clang does not seem to have this issue anymore in more recent versions, but it still does not support OpenMP.

## Configuration file¶

Since v1.2, galpy uses a configuration file to set a small number of configuration variables. This configuration file is parsed using ConfigParser/configparser. It is currently used:

• to set a default set of distance and velocity scales (ro and vo throughout galpy) for conversion between physical and internal galpy unit
• to decide whether to use seaborn plotting with galpy’s defaults (which affects all plotting after importing galpy.util.bovy_plot),
• to specify whether output from functions or methods should be given as an astropy Quantity with units as much as possible or not, and whether or not to use astropy’s coordinate transformations (these are typically somewhat slower than galpy’s own coordinate transformations, but they are more accurate and more general)
• to set the level of verbosity of galpy’s warning system (the default verbose=False turns off non-crucial warnings).

The current configuration file therefore looks like this:

[normalization]
ro = 8.
vo = 220.

[plot]
seaborn-bovy-defaults = False

[astropy]
astropy-units = False
astropy-coords = True

[warnings]
verbose = False


where ro is the distance scale specified in kpc, vo the velocity scale in km/s, and the setting is to not return output as a Quantity. These are the current default settings.

A user-wide configuration file should be located at $HOME/.galpyrc. This user-wide file can be overridden by a $PWD/.galpyrc file in the current directory. If no configuration file is found, the code will automatically write the default configuration to $HOME/.galpyrc. Thus, after installing galpy, you can simply use some of its simplest functionality (e.g., integrate an orbit), and after this the default configuration file will be present at $HOME/.galpyrc. If you want to change any of the settings (for example, you want Quantity output), you can edit this file. The default configuration file can also be found here.