# Installation¶

galpy can be installed using pip as:

pip install galpy


pip install -U --no-deps galpy


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).

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. A basic installation works with just the numpy/scipy/matplotlib stack. Some basic tests can be performed by executing:

nosetests -v -w nose/


## NEW in v1.2: 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_src/actionAngleTorus_c_ext/torus
cd galpy/actionAngle_src/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. On a Mac, the easiest way to install the GSL is using Homebrew as:

brew install gsl --universal


You should be able to check your version using:

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):

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


or:

setenv CFLAGS -I/usr/include
setenv LDFLAGS -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 and LDFLAGS defined you just have to add the '-I/usr/include' and '-L/usr/lib' to them.

### 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.

## NEW in v1.2: 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 units, 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). 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


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.