# Presentation: 199643

## Introduction to the Earth System Modeling Framework

- Don Stark _[stark@ucar.edu](mailto:stark@ucar.edu)_
- Gerhard Theurich _[gtheurich@sgi.com](mailto:gtheurich@sgi.com)_
- Shujia Zhou _[szhou@pop900.gsfc.nasa.gov](mailto:szhou@pop900.gsfc.nasa.gov)_
**May 24, 2006**

***Climate***

***Data ******Assimilation***

***Weather***

## Goals of this Tutorial

- To give future ESMF users an understanding of the background, goals, and scope of the ESMF project
- To review the status of the ESMF software implementation and current application adoption efforts
- To outline the principles underlying the ESMF software
- To describe the major classes and functions of ESMF in sufficient detail to give modelers an understanding of how ESMF could be utilized in their own codes
- To describe in steps how a user code prepares for using ESMF and incorporates ESMF
- To identify ESMF resources available to users such as documentation, mailing lists, and support staff

## For More Basic Information ...

**ESMF Website**
- _[http://www.esmf.ucar.edu](http://www.esmf.ucar.edu/)_
- See this site for downloads, documentation, references, repositories, meeting schedules, test archives, and just about anything else you need to know about ESMF.
- References to ESMF source code and documentation in this tutorial correspond to ESMF Version 2.2.2.

## 1 BACKGROUND, GOALS, AND SCOPE

*Overview*
- ESMF and the Community
- Development Status
- Exercises

## Motivation and Context

- In climate research and NWP... 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 ...development of first-generation frameworks, such as FMS, GEMS, CCA and WRF, that encourage software reuse and interoperability

## What is ESMF?

**What is ESMF?**

- ESMF provides tools for turning model codes into components with standard interfaces and standard drivers.
- ESMF provides data structures and common utilities that components use for routine services such as data communications, regridding, time management and message logging.

**ESMF GOALS**
- Increase scientific productivity by making model components much easier to build, combine, and exchange, and by enabling modelers to take full advantage of high-end computers.
- Promote new scientific opportunities and services through community building and increased interoperability of codes (impacts in collaboration, code validation and tuning, teaching, migration from research to operations)

## Application Example:  GEOS-5 AGCM

- Each box is an ESMF component
- Every component has a standard interface so that it is swappable
- Data in and out of components are packaged as state types with user-defined fields
- New components can easily be added to the hierarchical  system
- Coupling tools include regridding and redistribution methods

**Application Example:  GEOS-5 AGCM**

## Why Should I Adopt ESMF If I Already Have a Working Model?

- There is an emerging pool of other ESMF-based science components that you will be able to interoperate with to create applications - a framework for interoperability is only as valuable as the set of groups that use it.
- It will reduce the amount of infrastructure code that you need to maintain and write, and allow you to focus more resources on science development.
- ESMF provides solutions to two of the hardest problems in model development:  structuring large, multi-component applications so that they are easy to use and extend, and achieving performance portability on a wide variety of parallel architectures.
- It may be better software (better features, better performance portability, better tested, better documented and better funded into the future) than the infrastructure software that you are currently using.
- Community development and use means that the ESMF software is widely reviewed and tested, and that you can leverage contributions from other groups.

## 1 BACKGROUND, GOALS, AND SCOPE

- Overview
*ESMF and the Community*
- Development Status
- Exercises

## New ESMF-Based ProgramsFunding for Science, Adoption, and Core Development

**New ESMF-Based Programs****Funding for Science, Adoption, and Core Development**

| Modeling, Analysis and Prediction Program for Climate Variability and Change
Sponsor:  NASA
Partners:
University of Colorado at Boulder, University of Maryland, Duke University, NASA Goddard Space Flight Center, NASA Langley, NASA Jet Propulsion Laboratory,  Georgia Institute of Technology, Portland State University, University of North Dakota, Johns Hopkins University, Goddard Institute for Space Studies, University of Wisconsin, Harvard University, more
The NASA Modeling, Analysis and Prediction Program will develop an ESMF-based modeling and analysis environment to study climate variability and change.   |
| --- |

| Battlespace Environments Institute
Sponsor: Department of Defense
Partners:	
DoD Naval Research Laboratory, DoD Fleet Numerical, DoD Army ERDC, DoD Air Force Air Force Weather Agency
The Battlespace Environments Institute is developing integrated Earth and space forecasting systems that use ESMF as a standard for component coupling.  |
| --- |

| Integrated Dynamics through Earth’s Atmosphere and Space Weather Initiatives
Sponsors: NASA, NSFPartners: University of Michigan/SWMF, Boston University/CISM, University of Maryland, NASA Goddard Space Flight Center, NOAA CIRES
ESMF developers are working with the University of Michigan and others to develop the capability to couple together Earth and space  software components. |
| --- |

| Spanning the Gap Between Models and Datasets:Earth System Curator
Sponsor: NSFPartners:Princeton University, Georgia Institute of Technology, Massachusetts Institute of Technology, PCMDI, NOAA GFDL, NOAA PMEL, DOE ESG
The ESMF team is working with data specialists to extend and unify climate model and dataset descriptors, and to create, based on this metadata, an end-to-end knowledge environment. |
| --- |

## ESMF Impacts

- ESMF impacts a very broad set of research and operational areas that require high performance, multi-component modeling and data assimilation systems, including:
-   Climate prediction
-   Weather forecasting
-   Seasonal prediction
-   Basic Earth and planetary system research at various time and spatial scales
-   Emergency response
-   Ecosystem modeling
-   Battlespace simulation and integrated Earth/space forecasting
-   Space weather (through coordination with related space weather frameworks)
-   Other HPC domains, through migration of non-domain specific capabilities from
-     ESMF – facilitated by ESMF interoperability with generic frameworks, e.g. CCA

## Open Source Development

- Open source license (GPL)
- Open source environment (SourceForge)
- Open repositories: web-browsable CVS repositories accessible from the ESMF website
- for source code
- for contributions (currently porting contributions and performance testing)
- Open testing: 1500+ tests are bundled with the ESMF distribution and can be run by users
- Open port status: results of nightly tests on many platforms are web-browsable
- Open metrics: test coverage, lines of code, requirements status are updated regularly and are web-browsable

## Open Source Constraints

- ESMF does not allow unmoderated check-ins to its main source CVS repository (though there is minimal check-in oversight for the contributions repository)
- ESMF has a co-located, line managed Core Team whose members are dedicated to framework implementation and support – it does not rely on volunteer labor
- ESMF actively sets priorities based on user needs and feedback
- ESMF requires that contributions follow project conventions and standards for code and documentation
- ESMF schedules regular releases and meetings

- The above are necessary for development to proceed at the pace desired by sponsors and users, and to provide the level of quality and customer support necessary for codes in this domain

## 1 BACKGROUND, GOALS, AND SCOPE

- Overview
- ESMF and the Community
*Development Status*
- Exercises

## Latest Information

- For scheduling and release information, see:
- 	_[http://www.esmf.ucar.edu](http://www.esmf.ucar.edu/)_ > **Development**
- This includes latest releases, known bugs, and supported platforms.
- Task lists, bug reports, and support requests are tracked on the ESMF SourceForge site:
- 	_[http://sourceforge.net/projects/esmf](http://sourceforge.net/projects/esmf)_

## ESMF Development Status

- Overall architecture well-defined and well-accepted
- Components and low-level communications stable
- Rectilinear grids with regular and arbitrary distributions implemented
- Parallel regridding (bilinear, 1st order conservative) for rectilinear grids completed and optimized
- Parallel regridding for general grids (user provides own interpolation weights) in version 3.0.0
- Other parallel methods, e.g. halo, redistribution, low-level comms  implemented
- Utilities such as time manager, logging, and configuration manager usable and adding features
- Virtual machine with interface to shared / distributed memory implemented, hooks for load balancing implemented

## ESMF Platform Support

- IBM AIX (32 and 64 bit addressing)
- SGI IRIX64 (32 and 64 bit addressing)
- SGI Altix (64 bit addressing)
- Cray X1 (64 bit addressing)
- Compaq OSF1 (64 bit addressing)
- Linux Intel (32 and 64 bit addressing, with mpich and lam)
- Linux PGI (32 and 64 bit addressing, with mpich)
- Linux NAG (32 bit addressing, with mpich)
- Linux Absoft (32 bit addressing, with mpich)
- Linux Lahey (32 bit addressing, with mpich)
- Mac OS X with xlf (32 bit addressing, with lam)
- Mac OS X with absoft (32 bit addressing, with lam)
- Mac OS X with NAG (32 bit addressing, with lam)
- User-contributed g95 support
- Almost: NEC SX

## ESMF Distribution Summary

- Fortran interfaces and complete documentation
- Many C++ interfaces, no manuals yet
- Serial or parallel execution (mpiuni stub library)
- Sequential or concurrent execution
- Single executable (SPMD) and limited multiple executable (MPMD) support

## Some Metrics ...

- Test suite currently consists of
- ~2000 unit tests
- ~15 system tests
- ~35 examples
- 	runs every night on ~12 platforms
- ~291 ESMF interfaces implemented, ~278 fully or partially tested, ~95% fully or partially tested.
- ~170,000 SLOC

## ESMF Near-Term Priorities, FY06

- Usability!
- Read/write interpolation weights and more flexible interfaces for regridding
- Support for regridding general curvilinear coordinates and unstructured grids
- Reworked design and implementation of array/grid/field interfaces and array-level communications
- Grid masks and merges
- Basic I/O

## Planned ESMF Extensions

- Looser couplings:  support for multiple executable and Grid-enabled versions of ESMF
- Support for representing, partitioning, communicating with, and regridding unstructured grids and semi-structured grids
- Support for advanced I/O, including support for asynchronous I/O, checkpoint/restart, and multiple archival mechanisms (e.g. NetCDF, HDF5, binary, etc.)
- Support for data assimilation systems, including data structures for observational data and adjoints for ESMF methods
- Support for nested, moving grids and adaptive grids
- Support for regridding in three dimensions and between different coordinate systems
- Ongoing optimization and load balancing

## 1 BACKGROUND, GOALS, AND SCOPE

- Overview
- ESMF and the Community
- Development Status
*Exercises*

## Exercises

- Sketch a diagram of the major components in your application and how they are connected.
- Introduction of tutorial participants.

## Application Diagram

## 2 DESIGN AND PRINCIPLES OF ESMF

*Computational Characteristics of Weather and Climate*
- Design Strategies
- Parallel Computing Definitions
- Framework-Wide Behavior
- Class Structure
- Exercises

## Computational Characteristicsof Weather/Climate

**Computational Characteristics****of Weather/Climate**

- Mix of global transforms and local communications
- Load balancing for diurnal cycle, event (e.g. storm) tracking
- Applications typically require 10s of GFLOPS, 100s of PEs – but can go to 10s of TFLOPS, 1000s of PEs
- Required Unix/Linux platforms span laptop to Earth Simulator
- Multi-component applications:  component hierarchies, ensembles, and exchanges;components in multiple contexts
- Data and grid transformations between components
- Applications may be MPMD/SPMD, concurrent/sequential, combinations
- Parallelization via MPI, OpenMP, shmem, combinations
- Large applications (typically 100,000+ lines of source code)

***Platforms***

**assim**

**sea ice**

**ocean**

**land**

**atm**

**physics**

**dycore**

**assim_atm**

**atmland**

***Seasonal Forecast***

***coupler***

## 2 DESIGN AND PRINCIPLES OF ESMF

- Computational Characteristics of Weather and Climate
*Design Strategies*
- Parallel Computing Definitions
- Framework-Wide Behavior
- Class Structure
- Exercises

## Design Strategy:Hierarchical Applications

- Since each ESMF application is also a Gridded Component, entire ESMF applications can be nested within larger applications.  This strategy can be used to systematically compose very large, multi-component codes.

## Design Strategy:  Modularity

- Gridded Components don’t have access to the internals of other Gridded Components, and don’t store any coupling information.  Gridded Components pass their States to other components through their argument list.
- Since components are not hard-wired into particular configurations and do not carry coupling information, components can be used more easily in multiple contexts.

- atm_comp

- NWP application

- Seasonal prediction

- Standalone for basic research

## Design Strategy:  Flexibility

- Users write their own drivers as well as their own Gridded Components and Coupler Components
- Users decide on their own control flow

**Hub and Spokes Coupling**

**Pairwise Coupling**

## Design Strategy:Communication Within Components

- All communication in ESMF is handled within components.  This means that if an atmosphere is coupled to an ocean, then the Coupler Component is defined on both atmosphere and ocean processors.

- ocn_comp

- atm_comp

- processors

- atm2ocn _coupler

## Design Strategy:Uniform Communication API

- The same programming interface is used for shared memory, distributed memory, and combinations thereof.  This buffers the user from variations and changes in the underlying platforms.
- The idea is to create interfaces that are performance sensitive to machine architectures without being discouragingly complicated.
- Users can use their own OpenMP and MPI directives together with ESMF communications

- ESMF sets up communications in a way that is sensitive to the computing platform and the application structure

## 2 DESIGN AND PRINCIPLES OF ESMF

- Computational Characteristics of Weather and Climate
- Design Strategies
*Parallel Computing Definitions*
- Framework-Wide Behavior
- Class Structure
- Exercises

## Elements of Parallelism: Serial vs. Parallel

- Computing platforms may possess multiple processors, some or all of which may share the same memory pools
- There can be multiple threads of execution and multiple threads of execution per processor
- Software like MPI and OpenMP is commonly used for parallelization
- Programs can run in a serial fashion, with one thread of execution, or in parallel using multiple threads of execution.
- Because of these and other complexities, terms are needed for units of parallel execution.

## Elements of Parallelism: PETs 

- Persistent Execution Thread (PET)
- Path for executing an instruction sequence
- For many applications, a PET can be thought of as a processor
- Sets of PETs are represented by the Virtual Machine (VM) class
- Serial applications run on one PET, parallel applications run on multiple PETs

## Elements of Parallelism: Sequential vs. Concurrent

- In sequential mode components run one after the other on the same set of PETs.

## Elements of Parallelism: Sequential vs. Concurrent

- In concurrent mode components run at the same time on different sets of PETs

## Elements of Parallelism: DEs

- Decomposition Element (DE)
- In ESMF a data decomposition is represented as a set of Decomposition Elements (DEs).
- Sets of DEs are represented by the DELayout class.
- DELayouts define how data is mapped to PETs.
- In many applications there is one DE per PET.

## Modes of Parallelism:Single vs. Multiple Executable

- In  Single Program Multiple Datastream (SPMD) mode the same program runs across all PETs in the application - components may run sequentially or concurrently.
- In Multiple Program Multiple Datastream (MPMD) mode the application consists of separate programs launched as separate executables - components may run concurrently or sequentially, but in this mode almost always run concurrently

## 2 DESIGN AND PRINCIPLES OF ESMF

- Computational Characteristics of Weather and Climate
- Design Strategies
- Parallel Computing Definitions
*Framework-Wide Behavior*
- Class Structure
- Exercises

## Framework-Wide Behavior

- ESMF has a set of interfaces and behaviors that hold across the entire framework.  This consistency helps make the framework easier to learn and understand.
- For more information, see Sections 6-8 in the Reference Manual.

## Classes and Objects in ESMF

- The ESMF Application Programming Interface (API) is based on the object-oriented programming notion of a class.  A class is a software construct that’s used for grouping a set of related variables together with the subroutines and functions that operate on them. We use classes in ESMF because they help to organize the code, and often make it easier to maintain and understand.
- A particular instance of a class is called an object. For example, Field is an ESMF class. An actual Field called temperature is an object.

## Classes and Fortran

- In Fortran the variables associated with a class are stored in a derived type.  For example, an ESMF_Field derived type stores the data array, grid information, and metadata associated with a physical field.
- The derived type for each class is stored in a Fortran module, and the operations associated with each class are defined as module procedures. We use the Fortran features of generic functions and optional arguments extensively to simplify our interfaces.

## 2 DESIGN AND PRINCIPLES OF ESMF

- Computational Characteristics of Weather and Climate
- Design Strategies
- Parallel Computing Definitions
- Framework-Wide Behavior
*Class Structure*
- Exercises

## ESMF Class Structure

**ESMF Class Structure**

**DELayout**
- Communications

**State**
- Data imported or exported

**Bundle**
- Collection of fields

**GridComp**
- Land, ocean, atm, ... model

***F90***

***Superstructure***

***Infrastructure***

**Field**
- Physical field, e.g. pressure

**Grid**
- LogRect, Unstruct, etc.

***Data***

***Communications***

***C++***

**Regrid**
- Computes interp weights

**CplComp**
- Xfers between GridComps

**Utilities**
- Virtual Machine, TimeMgr, LogErr, IO, ConfigAttr, Base etc.

**Array**
- Hybrid F90/C++ arrays

**Route**
- Stores comm paths

**DistGrid**
- Grid decomposition

**PhysGrid**
- Math description

## 2 DESIGN AND PRINCIPLES OF ESMF

- Computational Characteristics of Weather and Climate
- Design Strategies
- Parallel Computing Definitions
- Framework-Wide Behavior
- Class Structure
*Exercises*

## Exercises

- Following instructions given during class:
- Login.
- Find the ESMF distribution directory.
- See which ESMF environment variables are set.
- Browse the source tree.

## 3 CLASSES AND FUNCTIONS

*ESMF Superstructure Classes*
- ESMF Infrastructure Classes:  Data Structures
- ESMF Infrastructure Classes:  Utilities
- Exercises

## ESMF Class Structure

**ESMF Class Structure**

**DELayout**
- Communications

**State**
- Data imported or exported

**Bundle**
- Collection of fields

**GridComp**
- Land, ocean, atm, ... model

***F90***

***Superstructure***

***Infrastructure***

**Field**
- Physical field, e.g. pressure

**Grid**
- LogRect, Unstruct, etc.

***Data***

***Communications***

***C++***

**Regrid**
- Computes interp weights

**CplComp**
- Xfers between GridComps

**Utilities**
- Virtual Machine, TimeMgr, LogErr, IO, ConfigAttr, Base etc.

**Array**
- Hybrid F90/C++ arrays

**Route**
- Stores comm paths

**DistGrid**
- Grid decomposition

**PhysGrid**
- Math description

## ESMF Superstructure Classes

- 	See Sections 12-16 in the Reference Manual.
- Gridded Component
- Models, data assimilation systems - “real code”
- Coupler Component
- Data transformations and transfers between Gridded Components
- State – Packages of data sent between Components
- Application Driver – Generic driver

## ESMF Components

- An ESMF component has two parts, one that is supplied by the ESMF and one that is supplied by the user. The part that is supplied by the framework is an ESMF derived type that is either a Gridded Component (GridComp) or a Coupler Component (CplComp).
- A Gridded Component typically represents a physical domain in which data is associated with one or more grids - for example, a sea ice model.
- A Coupler Component arranges and executes data transformations and transfers between one or more Gridded Components.
- Gridded Components and Coupler Components have standard methods, which include initialize, run, and finalize. These methods can be multi-phase.

## ESMF States

- All data passed between Components is in the form of States and States only
- Description/reference to other ESMF data objects
- Data is referenced so does not need to be duplicated
- Can be Bundles, Fields, Arrays, States, or name-placeholders

## Application Driver

- Small, generic program that contains the “main” for an ESMF application.

## 3 CLASSES AND FUNCTIONS

- ESMF Superstructure Classes
*ESMF Infrastructure Classes:  Data Structures*
- ESMF Infrastructure Classes:  Utilities
- Exercises

## ESMF Class Structure

**ESMF Class Structure**

**DELayout**
- Communications

**State**
- Data imported or exported

**Bundle**
- Collection of fields

**GridComp**
- Land, ocean, atm, ... model

***F90***

***Superstructure***

***Infrastructure***

**Field**
- Physical field, e.g. pressure

**Grid**
- LogRect, Unstruct, etc.

***Data***

***Communications***

***C++***

**Regrid**
- Computes interp weights

**CplComp**
- Xfers between GridComps

**Utilities**
- Virtual Machine, TimeMgr, LogErr, IO, ConfigAttr, Base etc.

**Array**
- Hybrid F90/C++ arrays

**Route**
- Stores comm paths

**DistGrid**
- Grid decomposition

**PhysGrid**
- Math description

## ESMF Infrastructure Data Classes

- 	Model data is contained in a hierarchy of multi-use classes.  The user can reference a Fortran array to an Array or Field, or retrieve a Fortran array out of an Array or Field.
- Array – holds a Fortran array (with other info, such as halo size)
- Field – holds an Array, an associated Grid, and metadata
- Bundle – collection of Fields on the same Grid bundled together for convenience, data locality, latency reduction during communications
- 	Supporting these data classes is the Grid class, which represents a numerical grid

## Grids

- See Section 25 in the Reference Manual for interfaces and examples.
- The ESMF Grid class represents all aspects of the computational domain and its decomposition in a parallel-processing environment It has methods to internally generate a variety of simple grids
- The ability to read in more complicated grids provided by a user is not yet implemented
- ESMF Grids are currently assumed to be two-dimensional, rectilinear horizontal grids, with an optional vertical grid whose coordinates are independent of those of the horizontal grid
- Each Grid is assigned a staggering in its create method call, which helps define the Grid according to typical Arakawa nomenclature.

## Arrays

- See Section 22 in the Reference Manual for interfaces and examples.
- The Array class represents a multidimensional array.
- An Array can be real, integer, or logical, and can possess up to seven dimensions. The Array can be strided.
- The first dimension specified is always the one which varies fastest in linearized memory.
- Arrays can be created, destroyed, copied, and indexed. Communication methods, such as redistribution and halo, are also defined.

## Fields

- See Section 20 in the Reference Manual for interfaces and examples.
- A Field represents a scalar physical field, such as temperature.
- ESMF does not currently support vector fields, so the components of a vector field must be stored as separate Field objects.
- The ESMF Field class contains the discretized field data, a reference to its associated grid, and metadata.
- The Field class provides methods for initialization, setting and retrieving data values, I/O, general data redistribution and regridding, standard communication methods such as gather and scatter, and manipulation of attributes.

## Bundles

- See Section 18 in the Reference Manual for interfaces and examples.
- The Bundle class represents “bundles” of Fields that are discretized on the same Grid and distributed in the same manner.
- Fields within a Bundle may be located at different locations relative to the vertices of their common Grid.
- The Fields in a Bundle may be of different dimensions, as long as the Grid dimensions that are distributed are the same.
- In the future Bundles will serve as a mechanism for performance optimization. ESMF will take advantage of the similarities of the Fields within a Bundle in order to implement collective communication, IO, and regridding.

## ESMF Communications

- See Section 27 in the Reference Manual for a summary of communications methods.
- Halo
- Updates edge data for consistency between partitions
- Redistribution
- No interpolation, only changes how the data is decomposed
- Regrid
- Based on SCRIP package from Los Alamos
- Methods include bilinear, conservative
- Bundle, Field, Array-level interfaces

## 3 CLASSES AND FUNCTIONS

- ESMF Superstructure Classes
- ESMF Infrastructure Classes:  Data Structures
*ESMF Infrastructure Classes:  Utilities*
- Exercises

## ESMF Class Structure

**ESMF Class Structure**

**DELayout**
- Communications

**State**
- Data imported or exported

**Bundle**
- Collection of fields

**GridComp**
- Land, ocean, atm, ... model

***F90***

***Superstructure***

***Infrastructure***

**Field**
- Physical field, e.g. pressure

**Grid**
- LogRect, Unstruct, etc.

***Data***

***Communications***

***C++***

**Regrid**
- Computes interp weights

**CplComp**
- Xfers between GridComps

**Utilities**
- Virtual Machine, TimeMgr, LogErr, IO, ConfigAttr, Base etc.

**Array**
- Hybrid F90/C++ arrays

**Route**
- Stores comm paths

**DistGrid**
- Grid decomposition

**PhysGrid**
- Math description

## ESMF Utilities

- Time Manager
- Configuration Attributes (replaces namelists)
- Message logging
- Communication libraries
- Regridding library (parallelized, on-line SCRIP)
- IO (barely implemented)
- Performance profiling (not implemented yet, may simply use Tau)

## Time Manager

- See Sections 32-37 in the Reference Manual for more information.
- Time manager classes are:
- Calendar
- Clock
- Time
- Time Interval
- Alarm
- These can be used independent of other classes in ESMF.

## Calendar

- A Calendar can be used to keep track of the date as an ESMF Gridded Component advances in time.  Standard calendars (such as Gregorian and 360-day) and user-specified calendars are supported. Calendars can be queried for quantities such as seconds per day, days per month, and days per year.

- Supported calendars are:
**Gregorian **The standard Gregorian calendar, proleptic to 3/1/-4800.
**no-leap **The Gregorian calendar with no leap years.
**Julian **The Julian calendar
**Julian Day **A Julian days calendar.
**360-day **A 30-day-per-month, 12-month-per-year calendar.
**no calendar **Tracks only elapsed model time in seconds.

## Clock and Alarm

- Clocks collect the parameters and methods used for model time advancement into a convenient package.  A Clock can be queried for quantities such as start time, stop time, current time, and time step. Clock methods include incrementing the current time, and determining if it is time to stop.
- Alarms identify unique or periodic events by “ringing” - returning a true value - at specified times. For example, an Alarm might be set to ring on the day of the year when leaves start falling from the trees in a climate model.

## Time and Time Interval

- A Time represents a time instant in a particular calendar, such as November 28, 1964, at 7:31pm EST in the Gregorian calendar. The Time class can be used to represent the start and stop time of a time integration.
- Time Intervals represent a period of time, such as 300 milliseconds. Time steps can be represented using Time Intervals.

## Config Attributes

- 	See Section 38 in the Reference Manual for interfaces and examples.
- ESMF Configuration Management is based on NASA DAO’s Inpak 90 package, a Fortran 90 collection of routines/functions for accessing *Resource Files *in ASCII format.
- The package is optimized for minimizing formatted I/O, performing all of its string operations in memory using Fortran intrinsic functions.

## LogErr

- 	See Section 39 in the Reference Manual for interfaces and examples.
- The Log class consists of a variety of methods for writing error, warning, and informational messages to files.
- A default Log is created at ESMF initialization. Other Logs can be created later in the code by the user.
- A set of standard return codes and associated messages are provided for error handling.
- LogErr will automatically put timestamps and PET numbers into the Log.

## Virtual Machine (VM)

- See Section 41 in the Reference Manual for VM interfaces and examples.
- VM handles resource allocation
- Elements are Persistent Execution Threads or PETs
- PETs reflect the physical computer, and are one-to-one with Posix threads or MPI processes
- Parent Components assign PETs to child Components
- The VM communications layer does simple MPI-like communications between PETs (alternative communication mechanisms are layered underneath)

## DELayout

- See Section 40 in the Reference Manual for interfaces and examples.
- Handles decomposition
- Elements are Decomposition Elements, or DEs
- DELayout maps DEs to PETs, can have more than one DE per PET (for cache blocking, user-managed OpenMP threading)
- Array, Field, and Bundle methods perform inter-DE communications
- Simple connectivity or more complex connectivity (for releases 3.0.0 and later, this connectivity information is stored in a public DistGrid class instead of DELayout)

## 3 CLASSES AND FUNCTIONS

- ESMF Superstructure Classes
- ESMF Infrastructure Classes:  Data Structures
- ESMF Infrastructure Classes:  Utilities
*Exercises*

## Exercises

- Change directory to $ESMF_DIR, which is the top of the ESMF distribution.
- Change directory to **build_config**, to view directories for supported platforms.
- Change directory to ../**src** and locate the** Infrastructure** and **Superstructure** directories.
- Note that code is arranged by class within these directories, and that each class has a standard set of subdirectories (doc, examples, include, interface, src, and tests, plus a makefile).
- Web-based alternative:
- Go to the sourceforge site:  _[http://sourceforge.net/projects/esmf](http://sourceforge.net/projects/esmf)_
- Select **Browse the CVS tree**
- Continue as above from number 2.   Note that this way of browsing the ESMF source code shows all directories, even empty ones.

## 4 RESOURCES

*Documentation*
*User Support*
*Testing and Validation Pages*
*Mailing Lists*
*Users Meetings*
- Exercises

## Documentation

- Users Guide
- Installation, quick start and demo, architectural overview, glossary
- Reference Manual
- Overall framework rules and behavior
- Method interfaces, usage, examples, and restrictions
- Design and implementation notes
- Developers Guide
- Documentation and code conventions
- Definition of compliance
- Requirements Document
- Implementation Report
- C++/Fortran interoperation strategy
- (Draft) Project Plan
- Goals, organizational structure, activities

## User Support

- All requests go through the _[esmf_support@ucar.edu](mailto:esmf_support@ucar.edu)__ list so that they can be archived and tracked_
- Support policy is on the ESMF website
- Support archives and bug reports are on the ESMF website -
- 	see _[http://www.esmf.ucar.edu](http://www.esmf.ucar.edu/)__ > _**Development**
- 	Bug reports are under **Bugs** and support requests are under **Lists**.

## Testing and Validation Pages

- Accessible from the **Development** link on the ESMF website
- Detailed explanations of system tests and use test cases
- Supported platforms and information about each
- Links to regression test archives
- Weekly regression test schedule

## Mailing Lists To Join

- esmf_jst@ucar.edu
- 	Joint specification team discussion
- Release and review notices
- Technical discussion
- Coordination and planning
- esmf_info@ucar.edu
- General information
- Quarterly updates
- esmf_community@ucar.edu
- Community announcements
- Annual meeting announcements

## Mailing Lists To Write

- esmf@ucar.edu
- 	Project leads
- Non-technical questions
- Project information
- esmf_support@ucar.edu
- Technical questions and comments

## 4 RESOURCES

- Documentation
- User Support
- Testing and Validation Pages
- Mailing Lists
- Users Meetings
*Exercises*

## Exercises

- Locate on the ESMF website:
- The Reference Manual, User’s Guide and Developer’s Guide
- The ESMF Draft Project Plan
- The current release schedule
- The modules in the contributions repository
- The weekly regression test schedule
- Known bugs from the last public release
- The % of public interfaces tested
- The ESMF support policy
- Subscribe to the ESMF mailing lists

## 5 PREPARING FOR AND USING ESMF

*Adoption Strategies*
- Quickstart
- Exercises

## Adoption Strategies: Top Down

- Decide how to organize the application as discrete Gridded and Coupler Components. The developer might need to reorganize code so that individual components are cleanly separated and their interactions consist of a minimal number of data exchanges.
- Divide the code for each component into initialize, run, and finalize methods. These methods can be multi-phase, e.g., init_1, init_2.
- Pack any data that will be transferred between components into ESMF Import and Export States in the form of ESMF Bundles, Fields, and Arrays.  User data must match its ESMF descriptions exactly.
- The user must describe the distribution of grids over resources on a parallel computer via the VM and DELayout.
- Pack time information into ESMF time management data structures.
- Using code templates provided in the ESMF distribution, create ESMF Gridded and Coupler Components to represent each component in the user code.
- Write a set services routine that sets ESMF entry points for each user component’s initialize, run, and finalize methods.
- Run the application using an ESMF Application Driver.

## Adoption Strategies: Bottom Up

- Adoption of infrastructure utilities and data structures can follow many different paths. The calendar management utility is a popular place to start, since for many groups there is enough functionality in the ESMF time manager to merit the effort required to integrate it into codes and bundle it with an application.

## 5 PREPARING FOR AND USING ESMF

- Adoption Strategies
*Quickstart*
- Exercises

## ESMF Quickstart

- Created when ESMF is compiled
- $ESMF_DIR/quick_start top level directory
- Contains a _makefile_ which builds the quick_start application
- Running it will print out execution messages to standard output
- Cat the output file to see messages

## ESMF Quickstart Structure

## ESMF Quickstart

- Directory contains the skeleton of a full application:
- 2 Gridded Components
- 1 Coupler Component
- 1 top-level Gridded Component
- 1 AppDriver main program
- A file for setting module names
- README file
- Makefile
- sample.rc resource file

## 5 PREPARING FOR AND USING ESMF

- Adoption Strategies
- Quickstart
*Exercises*

## Exercises

- Following the User’s Guide:
- Build and run the Quickstart program.
- Find the output files and see the printout.
- Add your own print statements in the code.
- Rebuild and see the new output
- For a more complex example...
- Find the description the more advanced Coupled Flow Demo in
- the User’s Guide.

## Answers to Section 4 Exercises

-        Starting from _[http://www.esmf.ucar.edu/](http://www.esmf.ucar.edu/)_ :
- The Reference Manual, User’s Guide and Developer’s Guide Downloads & Documentation -> ESMF Documentation List
- The ESMF Draft Project PlanManagement
- The current release scheduleHome Page Quick Links -> Release schedule
- The modules in the contributions repositoryUser Support & Community -> Entry Point to the ESMF Community Contributions Repository -> Go to Sourceforge Site
- The weekly regression test scheduleDevelopment -> Test & Validation

## Answers to Section 4 Exercises

-        Starting from _[http://www.esmf.ucar.edu/](http://www.esmf.ucar.edu/)__ :_
- Known bugs from the last public releaseHome Page Quick Links -> Download ESMF releases and view release notes and known bugs
- The % of public interfaces testedDevelopment -> Metrics
- The ESMF Support PolicyUser Support & Community -> Support Requests
- Subscribe to the ESMF mailing listsUser Support & Community -> ESMF Mailing Lists