Soma-workflow: A unified and simple interface to parallel computing resource

Parallel computing resources are now highly available: multiple core machines, clusters or grids. Soma-workflow is a unified and simple interface to parallel computing resources which aims at making easier the use of parallel resources by non expert users and software.

Soma-workflow is an open source Python application.


Overview of soma-workflow graphical user interface


Soma-Workflow is free software, and is distributed under the CeCILL-B licence, which is similar to the BSD licence (with precisions for the french law).

Quick start on a multiple core machine

  • Requirements: Python 2.7 or more. For the GUI: Qt version 4.6.2 or more, PyQt version 4.7.2 or more, or PySide version 1.1.1 or more and optionally matplotlib version 0.99 or more.

  • We recommend to install Soma-workflow in a local directory: no special rights required & easy clean up at any time removing the local directory.

    1. Create a local directory such as ~/.local/lib/python2.7/site-packages and create the bin directory: ~/.local/bin

    2. Setup the environment variables with the commands:

      $ export PYTHONPATH=$HOME/.local/lib/python2.7/site-packages:$PYTHONPATH
      $ export PATH=$HOME/.local/bin:$PATH

    You can copy these lines in your ~/.bashrc for an automatic setup of the variables at login.

  • Download the latest tarball from PyPI and expand it.

  • Install Soma-workflow in the ~/.local directory:

    $ python install --user

    If you chose a different name for you local directory (ex: ~/mylocal) use instead the following command:

    $ python install --prefix ~/mylocal
  • Run the GUI:

    $ soma_workflow_gui
  • Run the documentation examples.

Main Features

Unified interface to multiple computing resources:
Submission of jobs or workflows with an unique interface to various parallel resources: multiple core machines or clusters which can be managed by various systems (such as Grid Engine, Condor, Torque/PBS, LSF..)
Workflow management:

Soma-workflow provides the possibility to submit a set of tasks (called jobs) with execution dependencies without dealing with individual task submission.


Workflow example

Python API and Graphical User Interface:

The Python API was designed to be easily used by non expert user, but also complete to meet external software needs: submission, control and monitoring of jobs and workflows. The GUI provides an easy and quick way of monitoring workflows on various computing resources. The workflows can also be submitted and controlled using the GUI.


Overview of Soma-workflow python API


Overview of Soma-workflow graphical interface

Quick start on multiple core machines:
Soma-workflow is directly operational on any multiple core machine.
Transparent remote access to computing resources:
When the computing resource is remote, Soma-workflow can be used as a client-server application. The communication with a remote computing resource is done transparently for the user through a ssh port forwarding tunnel. The client/server architecture enables the user to close the client application at any time. The workflows and jobs execution are not stopped. The user can open a client at any time to check the status of his work.
File transfer and file path mapping tools:
If the user’s machine and the remote computing resource do not have a shared file system, Soma-workflow provides tools to handle file transfers and/or path name matchings.


In version 3.1:

  • The client/server communication architecture (based on ZMQ) has been revised to avoid some stability and timeout problems.
  • Dynamic parameters in workflows: jobs can now have “named parameters” and outputs produced by a job (number, string, filename) are passed to downstream jobs. While passing values from a job output to another job input, custom link functions can be called to transform values, enabling applications such as map/reduce, cross-validation or leave-one-out in a semi-dynamic way.

In version 3.0:

  • Pyro is gone, Soma-Workflow is now using ZMQ and PyZmq.

    As a consequence, all the client/server communication layer has been made completely incompatible with soma-workflow 2.9 and earlier. Client and server should always be the same version anyway. The client/server API has not changed fundamentally however.

  • Porting to Python3: Pyro3 having been dropped, all the requirements for porting to Python3 have now been met, and Soma-Workflow can entirely wotk using Python3. However it is not possible to run different versions of Python on the client and the server: read Important changes in Soma-Workflow 3 for details.

  • New PBSPro scheduler type, to be used when DRMAA is not available, or doesn’t work (like on our new cluster): use scheduler_type = pbspro in the server config file. It might also work on PBS/Torque, we have not tried yet.

  • It is now possible to restart a workflow which is still running: running / pending jobs will go on, and only failed jobs will be restarted.

  • A few improvements, such as the 2 new plots modes in the GUI (soma_workflow_gui) displaying the use of CPUs in addition to jobs (useful for parallel jobs)

See the full changelog


  • MICCAI 2011 workshop High Performance and Distributed Computing for Medical Imaging, September 22nd 2011, Toronto: paper, poster
  • Python in Neuroscience workshop satellite to Euroscipy, August 29-30 2011, Paris: abstract, presentation
  • HBM Annual Meeting 2011, Quebec: poster
They use Soma-workflow:

Authors and contributors

Yann Cointepas¹²

Benoit Da Mota³ - Major contributor of the MPI scheduler

Isabelle Denghien Courcol⁴

Clara Fischer²

Dominique Geffroy⁴

Soizic Laguitton² - Main developper (Jan 2010 to March 2013)

Jinpeng Li¹

Denis Rivière¹

Nicolas Souedet⁵

Thomas Vincent¹⁶

¹ CEA, Neurospin, Gif-sur-Yvette, France | ² CATI, France | ³ PARIETAL, INRIA, Saclay, France | ⁴ INSERM, Neurospin, Gif-sur-Yvette, France | ⁵ CEA, MIRCEN, Fontenay-aux-roses, France | ⁶ INRIA, MISTIS, Grenoble, France