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Cupid A Domain Specific Language

for Coupled ESMs

Rocky DunlapCoupling Workshop 2013

Second Workshop on Coupling Technologies for Earth System ModelingNCAR, Boulder, Colorado, February 20-22, 2013

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Outline

• Motivation and Goals of Cupid• Overview and Current Status• Example Application• Evaluation and Challenges• Future Work

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Motivation and Goals• Earth System Modeling software is highly

complex• Much effort is spent dealing with accidental

details of parallel programming, array manipulations, etc.

• Goal of Cupid:

Provide significant increases in modeler productivity by raising the level of abstraction of

the coupling aspects of ESMs.

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Different Kinds of Performance

# of nodes

days simulatedper hour

paperspublished

hours of effort

model scalabilitymodeler productivity

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Form of Reuse Programming Tasks Example TechnologiesSoftware Libraries

Instantiate library types; call library subroutines

MCT, PSMILe (OASIS), OASIS-MCT

Component Technologies

Write explicit interfaces; implementation via traditional programming; composition via interface “wiring”

CCA

Frameworks Same as library + implement fine-grained, pre-defined interfaces (due to inversion of control)

ESMF, CSDMS, OpenPALM

Generative/ Domain-specific languages

Programs written in a custom language with domain-specific concepts; textual or visual notations

BFG XML, PrePALM (OpenPALM), Cupid

How does the form of code reuse affect developer productivity?

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General Purpose Language (Fortran 90)

programmodule

if, then, else, endifdo, do while

callinteger, real, double precision

dimensionopen, read

continue, stop

Domain Specific Language

gridded componentcoupler component

driverstate

decompositiongrid, mesh

fieldredist, regrid

clock

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Cupid Overview

Coupling Specification(Cupid DSL)

Black box

Generated Application(Fortran 90)

ExecutableCupid

CompilerFortran

Compiler

White box

Maintenance Maintenance

ESMF

link

Black boxBlack boxBlack box

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Domain Model and Constraints class Superstructure

ESMFCouplerComponentESMFSimpleCouplerComponentESMFGriddedComponent

ESMFScope

ESMFNamedEntityESMFComponent

Infrastructure::ESMFScopedItem

Infrastructure::ESMFField

Infrastructure::ESMFStateItem

ESMFFieldConnection«invariant»{srcField must be contained in srcComponent;dstField must be contained in dstComponent}

dstComponent

1

srcComponent

1

*

children

*

1..*

srcField dstField

self.fieldConnection->forAll(srcField.scope = self.srcComponent and dstField.scope = self.dstComponent)

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Cupid Compiler[template public genESMFInitMethod(c : ESMFGriddedComponent)]subroutine init_(comp, istate, ostate, clock, rc)type(ESMF_GridComp) :: comptype(ESMF_State) :: istatetype(ESMF_State) :: ostatetype(ESMF_Clock) :: clockinteger, intent(out) :: rc

...[for (field : ESMFField | c.item->filter(ESMFField))][field.name/] = ESMF_FieldCreate(grid=[field.grid.name/], arrayspec=[field.arraySpec.name/], & indexflag=[field.index/], & totalLWidth=[toFortranArrayConstructor(field.totalLWidth)/], & totalUWidth=[toFortranArrayConstructor(field.totalUWidth)/], & name="[field.name/]", rc=rc)[/for]...[/template] MOF Model to Text

Transformation Language (OMG)http://www.omg.org/spec/MOFM2T/1.0/

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Eclipse-based ImplementationEclipse Modeling Framework

Ecore Metamodel

Acceleo Model to Text

Photran Editor

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Current StatusESMF Type Public API Methods DSL Generated Calls

ESMF_Array 22 2

ESMF_ArraySpec 4 1

ESMF_Clock 20 2

ESMF_CplComp 24 5

ESMF_DistGrid 10 1

ESMF_Field 27 9

ESMF_Grid 18 3

ESMF_GridComp 24 6

ESMF_State 18 4

ESMF_Time 16 1

ESMF_TimeInterval 18 2

(Framework level) 25 2

(12 Unsupported types) 161 0

387 38

Calls can be generated to ~10% of API

methods.

11 of 23 ESMF types

represented in DSL.

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CFlowDriv

er

CoupledFlowMod

FlowSolverM

od

InjectorM

od

CouplerMod

0

100

200

300

400500

600

700

800

900

1000

Lines of CodeGenerated and Hand Coded

Generated Skeleton

Complete (Generated + Hand Coded)

Line

s of C

ode

CFlowDriver

CoupledFlow

FlowSolver Coupler Injector

Case Study:ESMF Coupled

Flow Demo

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Caution: Some coding required!

Un-touched, 487, 35%

Inserted, 865, 63%

Modified, 31, 2%

Lines of Code

Inserted Code• reading namelists,

setting parameters• set up initial conditions

and boundary conditions

• field updates for each timestep

• calls to halo operations

Generated Code• static superstructure• instantiation of

components, states, and fields

• populating import and export states

• calls to child components

• coupler component (redist or regrid)

• freeing memory

Modified Code• grid coordinates• grid inheritance

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Challenge: DSL Integration• How to integrate with scientific code?• Possible solutions:

– Skeleton approach• Developer fills in science implementation

– Model interface approach• A set of Fortran subroutines with model fields as

subroutine arguments (à la BFG)• Define interfaces using Scientific Interface Description

Language (SIDL)• Self-describing models (à la CSDMS BMI)

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Challenge: Representing Behavior

• Static structural aspects are fairly easy to model– Parent-child relationship of components

• Behavioral (dynamic) aspects are more difficult– Populating an ESMF State object with different fields

during different points of model execution• Possible solutions

– make behaviors implicit (e.g., all fields added during init, remain unchanged during run, removed during finalize)

– introduce a behavioral modeling language (adds complexity!)

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Conclusion

SuperstructureComponents and their composition; driving

ScienceField updates based on discrete form of PDEs

InfrastructureBuilding blocks: grids, distributed fields, clocks,

regrid, redistribution, I/O, configuration, etc.

Different approaches and different tools are required to

raise the abstraction level of each of these

parts.

DSL approach is viable for specifying some parts of the coupling infrastructure.

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Future Work• Cupid: An IDE for Model Development and Modeler

TrainingNASA Computational Modeling Algorithms and Cyberinfrastructure (CMAC) Program

• Team– Georgia Institute of Technology (Dunlap/Mark/Rugaber)– University of Colorado/CIRES (DeLuca)– NASA Software Systems Support Office (Clune)– NASA GISS (Schmidt)

• Extend and harden existing DSL+generator into a student training environment for rapidly developing ESMF-based applications

• Incorporate more IDE features, including linking with an execution environment

• Modularize Model E and demonstrate in IDE

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Thanks!

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Domain Specific LanguagesIncrease Productivity

• Nokia [1] mobile phone app development – 1000% increase in productivity– “shift focus from code to design”– “In many cases, we can generate 100% of the required code.”

• US Air Force Military Command and Control Systems [2]– 300% increase in productivity

• Lucent Product Family development [3]– initial productivity factor 3x-5x; 10x productivity increase for

experts– graphical DSLs more successful than textual

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Reuse Techniques

System Specification

Generator

Compositional(library, components, frameworks)

Generative(domain-specific languages)

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CouplingSpecification

Generator

Hybrid Approach

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Challenge: Domain Model

• There is no universal domain model for coupling– SQL came about after a formal definition of

relational databases– Common Information Model (CIM) currently

defined as retrospective metadata– Jay Larson’s theory of coupling [4]

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Domain Model

Analysis

Strembeck, Mark, and Uwe Zdun. "An approach for the systematic development of domain‐specific languages." Software: Practice and Experience 39.15 (2009): 1253-1292.

Earth System Modeling

Framework(ESMF)

Core Language Model

Language Model Constraints

Behavioral Model

Approach: Extract DSL from an existing system

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You Have Already Used DSLsDSL Use

SQL Query and manipulate relational databases

Make, Ant Building software systems

Matlab Scientific data analysis

HTML Markup for web pages

YACC, ANTLR Parser generators

LATEX Typesetting

LabVIEW Design of measurement and control systems

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What kinds of domains benefit from DSLs?

Sprinkle, Jonathan, et al. "Guest Editors' Introduction: What Kinds of Nails Need a Domain-Specific Hammer?." IEEE Software 26.4 (2009): 15-18.

The domain is well-defined 40+ years of building coupled models

The domain has repetitive elements or patterns, such as multiple products, features, or targets

Emergence of reusable coupling software evidences common coupling requirements, designs, implementations

Accuracy; expert involvement; and flexibility of the specification, verification, and validation of design are important

Correct and verifiable coupling infrastructure is essential for scientific validity of model output

The implementation or specification must serve as documentation

Many ESMs are under-documented and often the code itself is the documentation.

Amortization of effort justifies investment in DSL creation.

Payoffs in terms of productivity increases when implementing new couplings

Domain characteristic Evidence in ESM domain

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Core Language Model pkg Superstructure

ESMFComponent

ESMFCouplerComponentESMFGriddedComponent

ESMFWorkspace

ESMFNamedEntity

ESMFScope

ESMFSimpleCouplerComponent

ESMFDriv er

ESMFFieldConnection

Infrastructure::ESMFScopedItem

*

*

children

srcComponent

1

dstComponent

1

1..*

*

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Core Language Model pkg Infrastructure

ESMFGrid

ESMFStateItem

ESMFField ESMFArray

ESMFDistGrid

ESMFState

ESMFScopedItem

ESMFClock

ESMFArraySpec ESMFRouteHandle ESMFTimeESMFTimeInterval

Superstructure::ESMFScope

*

*1

*

*

1

1 1* 1

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Object Constraint Language class Superstructure

ESMFCouplerComponentESMFSimpleCouplerComponentESMFGriddedComponent

ESMFScope

ESMFNamedEntityESMFComponent

Infrastructure::ESMFScopedItem

Infrastructure::ESMFField

Infrastructure::ESMFStateItem

ESMFFieldConnection«invariant»{srcField must be contained in srcComponent;dstField must be contained in dstComponent}

dstComponent

1

srcComponent

1

*

children

*

1..*

srcField dstField

self.fieldConnection->forAll(srcField.scope = self.srcComponent and dstField.scope = self.dstComponent)

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Implementation – Language Model

• Language model using Eclipse-based tools– classes, generalization/

specialization, abstract classes– type system– object references,

containment– OCL constraints via

annotations– automatic generation of

model editor GUI

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References1. Kelly, Steven, and Juha-Pekka Tolvanen. "Visual domain-specific modeling: Benefits

and experiences of using metaCASE tools." International workshop on Model Engineering, European Conference on Object-Oriented Programming (ECOOP) ed. J. Bezivin, J. Ernst. 2000.

2. Kieburtz, Richard B., et al. "A software engineering experiment in software component generation." Proceedings of the 18th international conference on Software engineering. IEEE Computer Society, 1996.

3. Weiss, D. M., and C. T. R. Lai. "Software product line engineering: a family based software engineering process." (1999).

4. J. Walter Larson, "Ten organising principles for coupling in multiphysics and multiscale models," ANZIAM J., 48, C1090-C1111 (2009).