CCSM ESMF Implementation and Evaluation Project

Name: Stage 3 ESMF Evaluation for CCSM

Mission Statement:

To perform a Stage 3 evaluation of the use of ESMF in CCSM by implementing a concurrent single executable using CAM, CLM, POP and CSIM gridded components. If Stage 3 evaluation is accepted, ESMF will be formally accepted for CCSM development for concurrent execution of CCSM.

Goals:

To create a flexible framework for a stand-alone CAM executable that can be run as either a sequential or concurrent application. This framework could then be used to incorporate CCSM ice and ocn active components instead of the CAM csim and docn surface components. The end result will be a reduction of duplication and code-maintenance while making CCSM a more powerful and useful scientific tool. This project will result in the construction new ESMF application drivers that will result in either sequentially or concurrent execution of CAM, CLM, POP and CSIM components.

On-Line Project Reports

• Stage-1 Release Schedule
• CCSMF ESMF Project Page

Motivation:

The long term goal of this project is the creation of a single executable SPMD implementation of the CCSM coupled model system which can run in either sequential or concurrent mode. There are numerous advantages to the creation of such a system:

• Scientific development across all model components (e.g. CAM, CLM, POP, CSIM) will occur on one model system. Currently, one version of thermodynamic CSIM is utilized for stand-alone CAM execution, whereas another version is utilized when running the CCSM model system.
• Code maintenance and testing will be greatly simplified. Currently, numerous models components are designed to be run in several modes. For example, CLM must be supported to run as an offline driver, as part of the CAM stand-alone executable and as a component of the CCSM model system. In a unified system, all model components will only be supported in one model.
• Code duplication will be greatly reduced. As an example, currently CLM maintains separate code to read in and utilize atmospheric NCEP data. Similarly, the CCSM coupled model also maintains a separate data model (latm) which reads in and uses atmospheric NCEP data. Creation of a unified coupled model will result in the removal of maintaining and testing for separate pieces of code that have the same functionality
• SPMD is a "sweet spot" for vendor tools. As a result, the creation of a SPMD coupled model will greatly simplify the process of error tracing and portability to new platforms. Performance monitoring will also be improved since performance tools are also normally designed to work with SPMD executables.

Authority:

Bill Collins

Project Lead:

Mariana Vertenstein

Scientific Lead:

None

Resources:

• Brian Eaton
• Brian Kauffman
• Erik Kluzek
• Mariana Vertenstein