IMAS – introduction to basic concepts

Key IMAS element: the Data Model

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First use case: User or code accessing Data Base through Access Layer

Interface Data Structures (IDS) to couple codes

• For Integrated Modelling, the Data Model also defines Interface Data Structures (IDS). These are structures within the Data Model that are used as standard interfaces between codes
• Solves the N2 problem (large number of components from various ITER members expected in IMAS)
• The usage of the IDSs makes the coupling of codes straightforward if they are in the same programming language
• The usage of the IDSs + AL allows coupling of codes even if they are not written in the same language
• The usage of the IDSs does NOT constrain your choice of coupling method. Codes can be coupled as:
  • Subroutines within a main program
  • Executables within a script
  • Components within a workflow engine

Second use case: codes coupled together directly (same language) or through AL (different languages)

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Workflow Engine and Component Generator to facilitate the development of Integrated Modelling workflows

• An Integrated Modelling simulation is described as a workflow with physics codes as components (modules)
• The workflow engine allows users to 
  • Design the workflow
  • Choose its components and tune their code-specific parameters
  • Execute the workflow
    
    
• The workflow engine will be used to help designing sophisticated workflows (e.g. Plasma Reconstruction chain, fully modularized Transport Solver, …)
  • It is intuitive enough for allowing “mere users” developping their own workflows
  • It hides the complexity of code coupling, data transfer, remote job submission, …
  • It allows sharing codes and workflows
  • It allows coupling to the PCS Simulation Platform
    
    
• Component generator: is a user tool that turns an IDS-compliant physics code into a component of the workflow

Physics codes + Data Access wrapped into a workflow component

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Workflow components coupled and executed within a workflow engine

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The layered structured: from the physics solver to the launcher

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• The structure is layered so that functionalities are clearly separated
• It is generic and independent of e.g. the launching script/workflow engine
  
  
• The Physics solver part (dark green) is not changed, it is not linked to the ITER Data Model. It may use the ITER Data Model internally or not.
• The architecture is identical to the case of a component called within a workflow engine
• The Physics Subroutine can be directly reused to generate a workflow component – the IMAS Infrastructure provides a tool that generates the component (pink part) automatically
  
  
• Exception: for codes handling massive amounts of data, Data Access is usually parallelised and must be done inside the physics_solver (no processor has enough memory to gather all data)

More details on the ITER Physics Data Model