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Introduction

Motivations

Complex simulations often combines a number of physics codes, potentially provided by various actors and written in different programming languages. To make them working together, an additional layer, that 'orchestrates' execution of particular codes, and takes care on passing data between 'producers' and 'consumers' is needed. Sometimes the functionality of such layer is provided by dedicated software (aka 'workflow orchestrators', like Kepler https://kepler-project.org/), sometimes it can be handled by much simpler mechanism like Python scripts.  Unfortunately all components ('actors') that constitute a computing scenario ('workflow') must be implemented in the same programming language, defining the same API.

Unfortunately, in most cases, scientific, simulation codes that performs computing intensive calculations  (due to performance reasons) are written in C++ or Fortran, while 'workflow orchestrators' are implemented in (more popular nowadays) languages, like Java, Python, etc. Hence the need for a 'wrapper' that intermediates between native code language and language of the orchestrator. Such wrappers can be developed manually, however users may benefit from a tool that automatise this process - iWrap

iWrap - actor generator

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iWrap is a modular component generator, implemented in Python, used for creating IMAS actors from physics models. This mechanism allows to integrate physics codes written in one language (Fortran, CPP) within complex computing scenarios designed in other language (e.g. Python).

It's plug-in based modular design with clear separation of concerns allows to generate various types of actors and easily change data access paradigm (from dataset descriptor for AL to direct HDC data for instance)

For user conveniency it provides two kinds of interfaces: user friendly graphical interface that allows non-experienced users to define an actor in intuitive way and command line interface foreseen for more advanced users that may want to e.g. automatise actor generation process using scripts.

Preparation of code

A signature of user code must follow strict rules to allow interaction between it and wrapping actor.  Please use following  >>link<< to get detailed guidelines for integration of native code into workflows using iWrap  

Native code description

iWrap, to properly wrap the code, needs detailed informations about both: the wrapped code and an actor to be generated. A formal description ot the code provides information about the programming language used, arguments passed to/from the code, type of these arguments, etc, etc, while an actor description tells iWrap how to name generated actor, where to put it, etc. Such descriptions has to be provided in YAML format file, prepared manually, or automatically with help of iWrap GUI.

 YAML file syntax

The YAML file consists of two documents, marked by tags corresponding to their roles: actor_description and code_description. Only code description part is mandatory, while 

 iWrap GUI

wrapping (job description, iWrap)

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