Workshop Charge J.C. Wells & M. Sato Park Vista Hotel Gatlinburg, Tennessee September 5-6, 2014

Workshop motivation We believe the workshop can play a seminal role in understanding the issues and possible collaborative opportunities between Japan and US for application co-design for exascale computing systems.

Major Workshop Goals & Outcomes The outcome of this workshop is a list of computational science challenges around which Japan and the US may form collaborative, exascale co-design research partnerships. –Solving these problems should have the potential to transform our understanding of science and its impacts and to improve our ability to apply knowledge in important applications. –This list should include challenge problems in the selected focus areas. Life science, drug design, health science data Materials by design Global change prediction for disaster prevention & mitigation Computational engineering Fundamental nuclear science Fusion energy sciences Research outcomes should advance exascale co-design goals, that is, inform the architectural design of extreme-scale application software and the computing systems on which these applications run.

Co-Design, from Wikipedia Co-design or codesign (CD) is a design process where professionals encourage, and guide users to develop solutions for themselves. CD is a development of systems thinking, which "begins when first you view the world through the eyes of another.”systems thinking CD in the different research fields is tightly connected to the conception or creation of artifacts in communities context through a shared vision, social learning and mutual understanding among all key stakeholders… The phrase co-design is also used in reference to the simultaneous development of interrelated software and hardware systems.

Difference of co-design between HPC and embedded apps, for example In embedded field, co-design sometimes, includes "specialization" for a particular applications. On the other hands, in HPC, the system will be shared by many applications. The co-design of HPC must optimize and maximize the benefits to cover many applications as possible. –Acknowledgment to Prof. M. Sato

How to approach your breakout session? The priority should be placed on identifying complementary, mutually beneficial science and engineering problems and research themes on which we can work together over the long term. Also, make clear what software and hardware elements are important for co-design in each topical application area. –The elements may include cache (size and bandwidth), network (latency and bandwidth), memory technologies, (e.g., high-bandwidth or hybrid memory cube), some specialized hardware, etc. –They also may include programming and runtime environments, and libraries

Overarching Questions (especially for Executive Breakout) How shall we build sustainable, multidisciplinary teams and research collaborations, including vendor partners, necessary to achieve our workshop goals? What are the appropriate collaborative agreements and organization to enable Japan and the US collaborate on exascale science application development in a mutually beneficial way? How are we going to maintain these collaborations over time?

Breakout Charge Questions: Intend for each breakout to answer the following questions to identify and advance a domain-specific co-design agenda. Identify questions to which the for co-design breakout members can contribute –Designate computer scientists from this group to participate with the 6 domain-science breakouts to assist in answering the questions and planning for a co-design research agenda.

Breakout Charge Questions, continued 1.What technical breakthroughs in science and engineering research can be enabled by exascale platforms and are attractive targets for Japan-US collaboration over the next 10 years? –Please prioritize discussions around opportunities for collaborative Japan-US R&D relationships.

Breakout Charge Questions, continued 2.What is the representative suite of applications in your research area, available today, which should form the basis of your co-design communication with computer architects? a)How are these applications currently constrained by compute and data resources, programming models, or available software tools? b)What are the gaps in available applications and application workflows, and requirements to fill these gaps? c)Which of these are ripe for collaboration within the context of Japan- US cooperation?

Breakout Charge Questions, continued 3.How can the application research community, represented by a topical breakout at this workshop, constructively engage the vendor community in co- design? a)How should these various aspects of the application and architecture be optimized for effective utilization of exascale compute and data resources? b)Consider all aspects of exascale application: formulation and basic algorithms, programming models & environments, data analysis and management, hardware characteristics.

Breakout Charge Questions, continued 4.How can you best manage the “conversations” with computer designers/architects around co-design such that (1) they are practical for computer design, and (2) the results are correctly interpreted within both communities? a)What are the useful performance benchmarks from the perspective of your domain? b)Are mini-apps an appropriate and/or feasible approach to capture your needs for communication to the computer designers? c)Are there examples of important full applications that are an essential basis for communication with computer designers? d)Can these be simplified into skeleton apps or mini-apps to simplify and streamline the co-design conversation

Breakout Charge Questions, continued 5.Describe the most important programming models and environment in use today within your community and characterize these as sustainable or unsustainable. a)Do you have appropriate methods and models to expose application parallelism in a high-performance, portable manner? b)Are best practices in software engineering often or seldom applied? c)Going forward, what are the critically important programming languages? d)On which libraries and/or domain-specific languages (DSL) is your research community dependent? e)Are new libraries or DSL’s needed in your research domain? f)Are these aspects of your programming environment sustainable or are new models needed to ensure their availability into the future?

Breakout Charge Questions, continued 6.Does your community have mature workflow tools that are implemented within leadership computing environments to assist with program composition, execution, analysis, and archival of results? If no, what are your needs and is their opportunity for value added? a)For example, do you need support for real-time, interactive workflows to enable integration with real-time data flows?

Breakout Charge Questions, continued 7.What are the new programming models, environments and tools that need to be developed to achieve our science goals with sustainable application software?

Breakout Charge Questions, continued 8.Is there a history, a track record in your research community for co-design for HPC systems in the installed machines in the past, and is there any co-design study done for these systems to document the effectiveness of co- design?