Fostering an international community to sustain the development of the ESPResSo software package

• Applicant: Professor Dr. Christian Holm
• Subject Area: Experimental and Theoretical Physics of Polymers ; Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics ; Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 391126171

The proposal aims at bringing the molecular dynamics software ESPResSo into a shape suitable for support by a global open source community. ESPResSo is mainly used for simulations in soft matter research and process engineering. It has reached the stage of a "demonstrator", as it has been used for research projects world wide resulting in numerous peer-reviewed publications. Initial steps towards long-term sustainability have been taken in that ESPResSo is open source (GPL) and available as source code through a public hosting service that also provides issue tracking and code review functionality. An important missing element in the long-term sustainability is a critical mass of core developers, in particular outside the group of the applicant. Hence, the primary goal of this proposal is to enhance ESPResSo's user base, and to significantly lower the barrier for users to become developers. To achieve this goal, a combination of measures from the areas of code development, documentation, teaching materials and outreach are planned.The development work is aimed both at usability and ease of extensibility. ESPResSo is currently controlled by a TCL scripting interface. Since TCL is outdated and does not interface well with other scientific software, a transition to Python was begun. Within this project, the Python interface is to be brought to production quality, by making it feature complete, and interoperable with other scientific software. The non-modular structure of ESPResSo's core makes it difficult for new developers to extend its functionality. To alleviate this, we plan to modularise the code and provide simple interfaces for common tasks. By removing unnecessary dependencies between different components, and by improving code clarity in key areas, we plan to reduce the number of regressions and errors caused by new code. Improvements to the user documentation aim at simplifying the introduction of users to ESPResSo. Part of this will be the creation of video tutorials guiding users through first steps, up to a simple simulation.To broaden the user base, we will provide ESPResSo based course modules for soft matter physics. Lectures based on this material will familiarise students with the software before they start their thesis work. Finally, we want to foster a global community of users and developers, which is able and willing to support ESPResSo long-term. To this end, an "ESPResSo delegate" will visit research groups, identify possible applications of ESPResSo, provide training, assist in development work, and help integrating new developments back into the code base. In summary, ESPResSo's long term sustainability will be ensured by significantly increasing the number of researchers who have a strong interest in its long term existence, and are capable of contributing to its core functionality. We want to achieve this through lowering the entry barrier for new users and by facilitating the transition from users to developers.

• DFG Programme: Research data and software (Scientific Library Services and Information Systems)