ESMF Town Hall Meeting AGU Fall Meeting 2010 San Francisco Gerhard Theurich, Fei Liu, Peggy Li, Cecelia DeLuca NOAA/CIRES December 15,

Outline Overview and Architecture Support and Extras Closer Look at Features Projects and Applications

Motivation In climate research and numerical weather prediction.. increased emphasis on detailed representation of individual physical processes; requires many teams of specialists to contribute components to an overall modeling system In computing technology... increase in hardware and software complexity in high-performance computing, as we shift toward the use of scalable computing architectures In software … emergence of frameworks to promote code reuse and interoperability The ESMF is a focused community effort to tame the complexity of models and the computing environment. It leverages, unifies and extends existing software frameworks, creating new opportunities for scientific contribution and collaboration.

Evolution Phase 1: NASA’s Earth Science Technology Office ran a solicitation to develop an Earth System Modeling Framework (ESMF). A multi-agency collaboration (NASA/NSF/DOE/NOAA) won the award. The core development team was located at NCAR. A prototype ESMF software package (version 2r) demonstrated feasibility. Phase 2: New sponsors included Department of Defense and NOAA. Many new applications and requirements were brought into the project, motivating a complete redesign of framework data structures (version 3r). Phase 3: The core development team moved to NOAA/CIRES for closer alignment with federal models. Basic framework development will be complete with version 5r (ports, bugs, feature requests, user support etc. still require resources). The focus is on increasing adoption and creating a community of interoperable codes.

Components ESMF is based on the idea of components – sections of code that are wrapped in standard interfaces Components can be arranged hierarchically, helping to organize the structure of complex models Different modeling groups may create different kinds or levels of components ESMF components in the GEOS-5 atmospheric GCM

Architecture Low Level Utilities Fields and Grids Layer Model Layer Components Layer Gridded Components Coupler Components ESMF Infrastructure User Code ESMF Superstructure MPI, NetCDF, … External Libraries ESMF provides a superstructure for assembling geophysical components into applications. ESMF provides an infrastructure that modelers use to – Generate and apply interpolation weights – Handle metadata, time management, data I/O and communications, and other functions – Access third party libraries

Standard Interfaces All ESMF components have the same three standard methods: – Initialize – Run – Finalize Each standard method has the same simple interface: call ESMF_GridCompRun (myComp, importState, exportState, clock, …) Where: myComp points to the component importState is a structure containing input fields exportState is a structure containing output fields clock contains timestepping information Steps to adopting ESMF Divide the application into components (without ESMF) Copy or reference component input and output data into ESMF data structures Register components with ESMF Set up ESMF couplers for data exchange Interfaces are wrappers and can often be set up in a non-intrusive way

Component Overhead Representation of the overhead for ESMF wrapped native CCSM4 component For this example, ESMF wrapping required NO code changes to scientific modules No significant performance overhead (< 3% is typical) Few code changes for codes that are modular Platform: IBM Power 575, bluefire, at NCAR Model: Community Climate System Model (CCSM) Versions: CCSM_4_0_0_beta42 and ESMF_5_0_0_beta_snapshot_01 Resolution: 1.25 degree x 0.9 degree global grid with 17 vertical levels for both the atmospheric and land model, i.e. 288x192x17 grid. The data resolution for the ocean model is 320x384x60.

Data Representation Options 1.Representation in index space (Arrays) One or more tiles store indices and topology Sparse matrix multiply for remapping with user supplied interpolation weights Highly scalable - no global information held locally, uses distributed directory approach (Devine 2002) for access to randomly distributed objects in an efficient, scalable way 2. Representation in physical space (Fields) Built on Arrays + some form of Grid Grids may be logically rectangular, unstructured mesh, or observational Remapping using parallel interpolation weight generation Also: ArrayBundles or FieldBundles, which group data for convenience and performance optimization Supported Array distributions

Metadata Handling and Usage Documentation of codes and data is critical as Earth system models are employed for decision making! Metadata is represented by the Attribute class as name/value pairs -Document data provenance -Automate some aspects of model execution and coupling Standard metadata is organized by Attribute packages -Aggregate, store, output in XML and other formats Attribute packages include the following conventions -Climate and Forecast (CF) -Select ISO standards -METAFOR Common Information Model (CIM) -These can be linked and nested

Applications of information layer Building an Information and Interoperability Layer Native model data structures Standard data structures Standard metadata Parallel generation and application of interpolation weights Run-time compliance checking of metadata and time behavior Fast parallel I/O Redistribution and other parallel communications Automated documentation of models and simulations (new) Ability to run components in workflows and as web services (new) Field Grid Clock Component Attributes: CF conventions, ISO standards, METAFOR Common Information Model Structured model information stored in ESMF wrappers User data is referenced or copied into ESMF structures modules fields grids timekeeping ESMF data structures

Outline Overview and Architecture Support and Extras Closer Look at Features Projects and Applications

Portability and Testing ESMF is comprehensively tested and extremely portable! Many tests and examples bundled with the software – About 4000 unit tests – An additional, automated test harness to cover the many options related to grids and distributions – Dozens of examples – Dozens of system tests – External demonstrations, showing ESMF linked to applications Users can separately download use test cases, with more realistic problem and data sizes Regression tests run nightly on 24+ platform/compiler combinations

Backwards Compatibility Following the next public release ESMF 5r, ESMF interfaces will be backwards compatible This will provide a solid platform for application development Some newer interfaces will not be included, for example – Location streams – Exchange grids Backwards compatibility will require the use of keywords (for example, rc=localrc) for optional arguments – Set up so users will know at compile time if this was not done

Where to Get Help Documentation and training materials Users Guide, comprehensive Reference Manuals Many examples and system tests Coming with public release 5r – Updated demonstration program – New web-based, user-friendly tutorial format If you’re stuck Write the support line, If you’re really stuck, we can usually arrange a call!

Outline Overview and Architecture Support and Extras Closer Look at Features Projects and Applications

Coupling options in ESMF Fortran or C components Single executable Multiple executable – Web service option – Top level MPMD Coupling communications can be called either from within a coupler or directly from a gridded component – useful when it is inconvenient to return from a component in order to perform a coupling operation Recursive components for nesting higher resolution regions Ensemble management with either concurrent or sequential execution of ensemble members

Grid Remapping Fast parallel computation of interpolation weights Weight generation is separate from weight application (sparse matrix multiply) for flexibility Supports grids that can be represented as combinations of triangular or rectangular elements, in 2D or 3D Bilinear, higher order finite element patch recovery (see below), or conservative interpolation options Pole options: n-point pole, full circle average, no pole Higher order method: – Khoei S.A., Gharehbaghi A. R. The superconvergent patch recovery technique and data transfer operators in 3d plasticity problems. Finite Elements in Analysis and Design, 43(8), – Hung K.C, Gu H., Zong Z. A modified superconvergent patch recovery method and its application to large deformation problems. Finite Elements in Analysis and Design, 40(5-6), 2004.

Remapping Performance ESMF parallel conservative remapping is scalable and accurate All ESMF interpolation weights are generated using unstructured finite element mesh Increases flexibility with 2D and 3D grids Adds overhead to bilinear interpolation Greatly improved performance over existing conservative methods Platform: Cray XT4, jaguar, at ORNL Versions: ESMF_5_2_0_beta_snapshot_07 and SCRIP 1.4 Resolution: - fv0.47x0.63: CAM Finite Volume grid, 576x384 - ne60np4: 0.5 degree cubed sphere grid, 180x180x6

Weight Generation Options Ways to generate interpolation weights: – Online Subroutine calls which calculate weights during run Can get weights or feed directly into ESMF sparse matrix multiply – Offline Application which generates a netCDF weight file from two netCDF grid files Summary of grid remapping options is posted at: /esmf_5_1_0_regridding_status.html

Performance of ESMF sparse matrix multiply Plot shows ESMF sparse multiply used in the Community Climate System Model (CCSM) for atmosphere to ocean grid remapping Comparable performance to native code, slightly better scaling at higher processor counts Versions: ESMF: 400rp2, CCSM: ccsm4_0_rel08 Resolution: f05_t12 (fv 0.47x0.63 atmosphere/land, tripole 0.1 ocean or 576x384 atmosphere/land and 3600x2400 ocean)

Noise reduction in CCSM transport Interp. noise Interpolation noise in a derivative of the zonal wind stress grid index in latitudinal direction ESMF higher order interpolation weights were used to map from a 2- degree Community Atmospheric Model (CAM) grid to an irregularly spaced POP ocean grid (384x320) dTAUx/dy was computed using interpolated fields – this is closely related to the curl of the wind stress, which drives the upper ocean circulation Noise is calculated as deviation of a point from the sum of itself plus four neighbors 33% reduction in noise globally compared to original bilinear interpolation (Image generated by NCAR CGD Oceanography section) Black = bilinear Red = higher-order ESMF v3.1.1 Green = higher order ESMF v4.0.0

Parallel I/O I/O is increasingly a bottleneck in high resolution simulations ESMF parallel I/O based on the PIO library developed by NCAR/DOE Integrated so that the user only sees ESMF data types: – ESMF_ArrayRead(), ESMF_ArrayWrite() – ESMF_FieldRead(), ESMF_FieldWrite() NetCDF and binary formats See: PIO User’s Guide,

Timekeeping Clocks – startTime, stopTime, runDuration, timeStep, many other properties – Forward and reverse modes for running clocks Alarms – Unsticky (turn themselves off after ringing) or sticky alarms TimeInterval and Time data types with many operators (+,-,/,==, more)

Summary of Features Fast parallel remapping: unstructured or logically rectangular grids, 2D and 3D, using bilinear, higher order, or conservative methods, integrated (during runtime) or offline (from files) Core methods are scalable to tens of thousands of processors Supports hybrid (threaded/distributed) programming for optimal performance on many computer architectures Multiple coupling and execution modes for flexibility Time management utility with many calendars, forward/reverse time operations, alarms, and other features Metadata utility that enables comprehensive metadata to be written out in standard formats Runs on 24+ platform/compiler combinations, exhaustive test suite and documentation Couples Fortran or C-based model components

ESMF 5r Represents completion of basic ESMF functions Expected early next year – alpha versions out

Outline Overview and Architecture Support and Extras Closer Look at Features Projects and Applications

A Common Model Architecture Increasingly, models in the U.S. follow a common architecture Atmosphere, ocean, sea ice, land, and/or wave models are components called by a top- level driver/coupler Components use ESMF or ESMF-like interfaces (see left) Many major U.S. weather and climate models either follow this architecture (CCSM/CESM, COAMPS, NEMS), want to follow this architecture for future coupled systems (NOGAPS), or have a different style of driver but could provide components to this architecture (GEOS-5, FMS) Even non-ESMF codes now look like ESMF … ESMF: ESMF_GridCompRun(gridcomp, importState, exportState, clock, phase, blockingFlag, rc) CESM (non-ESMF version): atm_run_mct(clock, gridcomp, importState, exportState) (argument names changed to show equivalence) WRF HYCOM CICE Ice POP Ocean CCSM4/CESM NMM-B Atm PhysNMM-B Atm Dynamics NEMS NMM History GFS Atm PhysGFS Atm Dynamics GFS GFS I/O FV Cub Sph Dycore GEOS-5 GWDGEOS-5 FV Dycore GEOS-5 Atm Dynamics GEOS-5 GSI GEOS-5 Moist Proc GEOS-5 Turbulence GEOS-5 LW RadGEOS-5 Solar Rad GEOS-5 Radiation GEOS-5 Aeros Chem GOCART Strat Chem Param Chem GEOS-5 Atm Chem GEOS-5 Ocean Biogeo GEOS-5 Salt Water Poseidon GEOS-5 Data Ocean GEOS-5 OGCM GEOS-5 Topology GEOS-5 Land Ice GEOS-5 Lake GEOS-5 Veg Dyn GEOS-5 Catchment GEOS-5 Land GEOS-5 Surface GEOS-5 Atm Physics GEOS-5 Hiistory ESMF Model Map 2010 NOAA Department of Defense University NASA Department of Energy National Science Foundation ESMF coupling complete Component (thin lines) Model (thick lines) Legend Ovals show ESMF components and models that are at the working prototype level or beyond. Tracer Advection CLM LandCAM Atm FIM Land Info System HAF GAIM MOM4 SWAN ADCIRCpWASH123 COAMPS WWIII NCOM NOGAPS

A Common Model Architecture The U.S. Earth system modeling community is converging on a common modeling architecture Atmosphere, ocean, sea ice, land, wave, and other models are ESMF or ESMF- like components called by a top-level driver or coupler Some models are modularizing further with nested components A Common Model Architecture

Common Model Architecture in Climate Metadata CMIP5 metadata display in Earth System Grid, developed by the Earth System Curator project in collaboration with E.U. METAFOR

From Common Model Architecture to Interoperability ESMF component interfaces alone do not guarantee technical interoperability – ESMF can be implemented in multiple ways Also need: – A common physical architecture – the scope and relationships of physical components (e.g. land surface as subroutine or component?) – Metadata conventions and usage conventions (e.g. who can modify component data?) – The next steps for modeling infrastructure involve encoding these conventions in software tools and templates

National Unified Operational Prediction Capability National Unified Operational Prediction Capability (NUOPC) is a consortium of operational weather prediction centers Developing a standard implementation of ESMF across NASA, NOAA, Navy, Air Force and other modeling applications Defining a target level of interoperability involving multiple aspects of code – EXAMPLES: Component interface. Components have a standard calling interface to facilitate generic drivers and communication protocols. Standardization does not include specification of what specific fields are actually in the import and export state. Timekeeping. Metadata and conventions for timekeeping enable modelers to understand without code inspection whether components can be coupled together. From: Final Report from the National Unified Operational Prediction Capability (NUOPC) Interim Committee on Common Model Architecture (CMA), June 18, 2009.

NUOPC Compliance Checker Designed as a way to encode and check conventions Can be linked in or not at run-time Presence of standard ESMF Initialize, Run, and Finalize methods and the number of phases in each Timekeeping conforms to NUOPC conventions Fields or FieldBundles (not Arrays/ArrayBundles) are passed between Components Which Fields are passed through import States and export States Required Component and Field metadata is present

Global Interoperability Program Global Interoperability Program (sponsor NOAA) – Support for multi-agency projects that cross domain boundaries and integrate along modeling workflows – Supports ESMF (and other) development and applications – New work with ESMF includes exploration of: self-documenting, end-to- end workflows integration and interfacing with other frameworks increasing usability new computing platforms and algorithms ESMF-enabled CCSM workflow implemented using Kepler