1. CSWIM Framework and Software Randall Bramley Indiana University

2. Overview • Bad news • Taking a code running on limited number of sites and turning into a community resource is hard • Documentation and support specifications are necessary • Good news • We can do this: right people, right tools, right time • Introduces new capabilities for plasma research that no one else will have (but a lot of up-front investment needed) • Some basic terminology … Fusion Simulation Project

3. A Component Architecture is • A set of objects called components, and the rules that govern their interactions called interfaces Fusion Simulation Project

4. Framework Has Different Meanings • General software composition environment • Examples: CCA, CORBA Component Model, … • A problem-solving environment for applications in a particular domain (numerical relativity, computational chemistry, …) • Earth System Modeling Framework • Computational Facility for Reacting Flow Science • A workflow management system • Example: Kepler • Integrated data analysis and visualization environments • More loosely, an informal environment for composing applications from subparts Fusion Simulation Project

5. Components, Ports, Interfaces • A component is some collection of functionality (a subroutine, a library, a complete code) • Components have publishedinterfacesspecifying how other components may interact with them • How the component implements its functionality is hidden • Components may interact with world without using interfaces: I/O to files, MPI communications, … • A portis a collection of methods (OO-speak for functions or subroutines). We’ll drop this intermediate idea, it’s not needed here Fusion Simulation Project

6. Overture Overture ISIS++ ISIS++ NWGrid NWGrid Trilinos Trilinos MOAB MOAB PETSc PETSc Mesquite Mesquite GRUMMP GRUMMP Frontier Frontier FMDB FMDB TSTT Unstructured Mesh Interface Linear Solver Interface Basic Motivation (from TSTT/TOPS) Interfaces Fusion Simulation Project

7. Components and Interfaces GetDistribution GetState GetState InitializeState SetState SetState LockState • Components provide or use one or more interfaces • As long as the interfaces don’t change, you can do anything you like on the inside • Or use any Equilibrium Advancer with that has the same interfaces as the community agrees upon. EquilibriumAdvancer Plasma State Comp Fusion Simulation Project

8. Components, Interfaces, CSWIM • We are going to adapt a more informal and flexible approach • Use ideas of components and interfaces, but we are forging into new territory here • We’ll use what’s useful and helpful • We’ll help guide the CS software component world to handle this kind of new community effort • I’ll use framework for the overall execution system, components for the computational parts, and infrastructure for shared utilities Fusion Simulation Project

9. Stages to Get Where We Need to Be

10. Stage 1: define components and their interfaces at least informally • A component need not be an existing code • CSWIM design is for it to represent a category of codes, or smaller utilities • One code may provide the services specified by multiple components. • Vital that we not define a component in terms of what code XYZ does • Avoid encumbering interface definitions with some cool, useful, but unique capability code XYZ has • Make it a subclass of the general interface, or • make it a separate interface Fusion Simulation Project

11. Stage 2: define components and their interfaces formally • Best: use Scientific Interface Definition Language (SIDL) • Minimally provide as a Fortran 2003 module, or subroutine with argument list declarations which can then be translated into SIDL • Reason for SIDL • Provides formal definition • Has a parse-check mechanism to verify semantics • Can have stubs automatically generated for implementations in Fortran95, Fortran77, C/C++, Java, Python, … Fusion Simulation Project

12. Stage 3: Compromises with reality • Perhaps no code yet provides interface IJK but we can modify it to something existing codes provide • Data translators, conversions should be separate components • As simple as interpolating between two finite difference mesh representations of a field • As complex as taking a field represented in spectral space, handing off to a real space finite element or PIC representation • May need to compromise/prioritize on these convertors Fusion Simulation Project

13. Stage 4: Implement the interfaces • This page intentionally blank in IBM-speak Fusion Simulation Project

14. Stage 5: Connect communicating components via file I/O • Component XYZ executes • Component XYZ writes data per interface spec • Framework service notified writing completed • Framework moves files to where “next” component needs them • Component UVW started, reads in data from file per interface spec • Lather, rinse, repeat Fusion Simulation Project

15. Stage 5.5: Connect communicating components via parallel file I/O • File I/O carried out in parallel • File transfer is done via parallel ftp or other HPC protocol Fusion Simulation Project

16. Stage 6: Live connections w/o writing/reading to/from hard drives • A change that should not be visible to the application user • Uses virtual serialization Fusion Simulation Project

17. What do we owe each other? • Framework using a script/portal interface • Launch executables on “suitable” platform • Monitor and inform you of job status (statii?) • Track and move data as needed • Connecting components with shared interface • Infrastructure services • Parallel/serial I/O interface for initial coupling • Linear solver interface to access advanced solvers • Centralized simulation time services ? • Shared/reusable data convertors ? Fusion Simulation Project

18. What do we owe each other? • The interface definitions • Done right, this is much harder than you think • Done right, it will clarify much thinking • Aids to sharing/running codes by others • Invoices of what executable components expect and require for input files, output locations, parameter settings, run-time libraries, … • Documentation, and codes must be runnable by nonexperts and as portable as possible • Version control use, contact person for problems • Much of what NTCC worked towards .. But now for parallel HPC systems. Fusion Simulation Project

19. Interfaces are an Investment • The larger the community, the greater the time & effort required to obtain agreement • True in component and non-component environments • MPI 1.0 took 1.5 years of regular meetings • CCSM/ESMF are still evolving after 10 years • Formality of “standards” process will increase with time – but now imperative is to get physics done along with the software development Fusion Simulation Project

20. Interfaces are an Investment • Biggerstaff’s Rule of Threes (from Gary Kumfert) • Must look at at least three systems to understand what is common (reusable) • Reusable software requires three times the effort of usable software • Payback only after third release • Bramley’s addendum • May take three years before system becomes productive • May provide the team with three times the capabilities of competitors • Mike Normans Corollary • Ultimately places apps scientist two years ahead of competitors Fusion Simulation Project