Install and Basic Usage

Installation

There are several ways to install and run Ganga:

NOTE - Currently Ganga is only available for python3 releases and supported on Linux distributions.

CVMFS

If you have access to CVMFS, Ganga can be found at /cvmfs/ganga.cern.ch/. This will be kept up-to-date with the latest release that you can run directly with:

/cvmfs/ganga.cern.ch/runGanga.sh

This isn’t just a link to the start-up script because it needs to be run from the correct directory. However, it will take all the command line options that the normal ganga script takes.

PyPI Install

You can also install directly from PyPI using:

pip install ganga

If you don’t have System Administrator rights or just want to do a private install then it can be beneficial to run using a virtualenv:

# Create a virtualenv
virtualenv -ppython3 gangaenv
cd gangaenv/
. bin/activate
# Install Ganga
pip install ganga

To install pip locally if it’s not on your system and you don’t have admin access please consult: https://pip.pypa.io/en/stable/installing/

Alternatively if you want you can install it using pip to your local user environment (not recommended if you have many python projects/libraries around)

pip install ganga --user

From Github

You can always install Ganga’s most recent commit at the time of writing by running

pip install -e git+git://github.com/ganga-devs/ganga.git#egg=ganga

If you don’t have System Administrator rights or just want to do a private install then it can be beneficial to run using a virtualenv:

# Create a virtualenv
virtualenv -ppython3 gangaenv
cd gangaenv/
. bin/activate
# Install Ganga
pip install -e git+git://github.com/ganga-devs/ganga.git#egg=ganga

Starting Ganga

As described above, to run Ganga simply execute ganga (for PyPI install), <installdir>/bin/ganga (for other installs) or the helper script in CVMFS. This will start Ganga and it’s associated threads as well as provide you with a Ganga IPython prompt that gives you access to the Ganga Public Interface (GPI) on top of the usual IPython functionality:

Note that the first time you run Ganga it will ask you to create a default .gangarc file which you should probably do. In the future, if you want to recreate this default config file, add the option -g to the command line.

Getting Help

The documentation for all objects and functions in Ganga can be accessed using the help system:

[13:25:29]
Ganga In [1]: help()
************************************

*** Welcome to Ganga ***
Version: 6.1.16
Documentation and support: http://cern.ch/ganga
Type help() or help('index') for online help.

This is free software (GPL), and you are welcome to redistribute it
under certain conditions; type license() for details.



This is an interactive help based on standard pydoc help.

Type 'index'  to see GPI help index.
Type 'python' to see standard python help screen.
Type 'interactive' to get online interactive help from an expert.
Type 'quit'   to return to Ganga.
************************************

help>

Now typing index at the prompt will list all the objects, etc. available. You can also directly access the documentation for an object using help directly:

help(Job)

You also have IPython’s tab-complete service available to help identify members of an object.

Hello World with Ganga

We are now in a position to submit our first job. This will take the defaults of the Ganga Job object which is to run echo 'Hello World' on the machine you’re currently running on:

j = Job()
j.submit()

If all goes well, you should see the job submit:

Ganga In [6]: j.submit()

Ganga.GPIDev.Lib.Job               : INFO     submitting job 0
Ganga.GPIDev.Lib.Job               : INFO     job 0 status changed to "submitting"
Ganga.Lib.Executable               : INFO     Preparing Executable application.
Ganga.Lib.Executable               : INFO     Created shared directory: conf-5bdd5d5a-07ce-4332-acbc-f0ab23ca7012
Ganga.GPIDev.Lib.Job               : INFO     Preparing subjobs
Ganga.GPIDev.Adapters              : INFO     submitting job 0 to Local backend
Ganga.GPIDev.Lib.Job               : INFO     job 0 status changed to "submitted"

Ganga Out [6]: 1

If you wait a few seconds and then press Enter you should then see that the job has already transitioned through running and to completed:

Ganga In [7]:

Ganga.GPIDev.Lib.Job               : INFO     job 0 status changed to "running"
Ganga.GPIDev.Lib.Job               : INFO     Job 0 Running PostProcessor hook
Ganga.GPIDev.Lib.Job               : INFO     job 0 status changed to "completed"

[13:34:10]
Ganga In [7]:

You can view the job in your repository using the jobs command which lists all job objects that Ganga knows about:

Ganga In [7]: jobs
Ganga Out [7]:

Registry Slice: jobs (1 objects)
--------------
    fqid |    status |      name | subjobs |    application |        backend |                             backend.actualCE |                       comment
-------------------------------------------------------------------------------------------------------------------------------------------------------------
       0 | completed |           |         |     Executable |          Local |                       epldt017.ph.bham.ac.uk |


[13:34:37]
Ganga In [8]:

You can get more info about your job by selecting it from the repository:

jobs(0)

You can also select specific info about the job object, e.g. the application that was run:

jobs(0).application

To check the stdout/stderr of a job, you can use a couple of methods:

jobs(0).peek('stdout', 'more')
j = jobs(0)
!more $j.outputdir/stdout

Job Monitoring

While Ganga is running in interactive mode, a background thread goes through all your active jobs and checks to see what state they are in. Generally, jobs will transition from new -> submitted -> running -> completed/failed. As described above, the jobs command will show you the state of your jobs in the Ganga repository.

In addition to this monitoring, there is also a web GUI provided that can be started using the --webgui option which gives a graphical representation of your repository. [NOTE THIS NEEDS TESTING AND MAY NOT WORK AT PRESENT!]

Scripting and Batch Mode

You can put your ganga commands into a python script and then execute it from the Ganga prompt like this:

open('submit.py', 'w').write("""
)
()

exec(compile(open('submit.py').read(), 'submit.py', 'exec'))

In addition, Ganga can be run in batch mode by just providing a script as the last argument:

ganga submit.py
/cvmfs/ganga.cern.ch/runGanga.sh submit.py

Note that by default, the monitoring is turned off while in batch mode.