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C-Coupler1: a Chinese community coupler for Earth system modeling

C-Coupler1 is a powerful coupling software for Earth system modeling with features such as flux computation, 3-D coupling, and modularization. It aims to provide a user-friendly, reliable, and reproducible platform for simulating and studying climate systems.

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C-Coupler1: a Chinese community coupler for Earth system modeling

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  1. C-Coupler1: a Chinese community coupler for Earth system modeling Li Liu, Cheng Zhang, Ruizhe Li, Guangwen Yang, Bin Wang, Zhiyuan Zhang Tsinghua University, China liuli-cess@tsinghua.edu.cn http://c-coupler.org/index.action

  2. Outline • C-Coupler development • C-Coupler1 • Bitwise identical reproducibility • Future work

  3. Milestones of C-Coupler development

  4. Target functions of C-Coupler • Science • Flux computation • 3-Dcoupling • Two-way model nesting and interactive ensemble • Technology • Modularization, extendibility • High parallel efficiency • Application • Powerful coupling functions, user friendliness • Reliability, automatic error detection • Reproducibility of simulation results

  5. Architecture of models with C-Coupler ATM ICE C-Coupler Coupler component LND OCN

  6. Software structure of C-Coupler Standardized component models Component models code Component models configuration … ATMs OCNs LNDs ICEs Carbon Configuration system Coupled models configuration Interfaces Interfaces Coupling flow configuration Process MGR Communication MGR Grid MGR Remapping MGR Restart MGR Decomposition MGR Coupling generator Coupling generator Runtime configuration Time MGR Data MGR Runtime software system C-Coupler runtime software system External coupling algorithms Remapping algorithms Scientific algorithms I/O algorithms

  7. Software modules Input data Standardized component models External algorithms Runtime configuration files of experiment models C-Coupler Create case From a default setting From an existing setting Experimental setting package Namelist Parallel settings Compiling options Configure Initial or restart Output settings Start and stop time Compile Run case Output data

  8. Outline • C-Coupler development • C-Coupler1 • Bitwise identical reproducibility • Future work

  9. C-Coupler1 • C-Coupler runtime software system for 3-D coupling (in C++) • CoR1.0: A common multi-dimensional remapping software for remapping, grid and field data management • Coupling interfaces (Fortran and C++) • Function managers, e.g., time manager, communication manager, etc. • Parallelization • C-Coupler platform: a runtime environment for model development, simulation and reproducibility • Runtime configuration for the CPL6 coupling flow • Imported: CPL6 flux algorithms

  10. Metadata for runtime configuration • Timer • <unit of frequency, count of frequency, count of delay> • Field instance • <field name, component name, parallel decomposition, grid name>

  11. Metadata for runtime configuration • External algorithm

  12. Metadata for runtime configuration • runtime algorithm list • Runtime procedure

  13. Data transfer and interpolation • Data transfer • All fields (of different data types, on different grids, on different parallel decompositions, or with different dimensions) to be transferred at the current time step can be packed into one message • 3-D interpolation • 2-D+1-D implementation • Spline is supported for 1-D interpolation • Offline and online • Parallel dynamic 3-D interpolation now (for example, for coupling between AGCM and atmospheric chemistry model)

  14. Example: parallel 2D flux coupling, global coupling, climate system model GAMIL2 LICOM2 C-Coupler1 CLM3 CICE4_LASG FGOALS-gc

  15. Coupler component in FGOALS-gc

  16. Example: Sharing platform for GAMIL development FGOALS-gc-colm … FGOALS-gc GAMIL CLM2 GEOS-Chem CLM3 CLM4 CoLM C-Coupler platform

  17. Example: parallel 3-D coupling, regional coupling, direct coupling WRF Direct coupling 2D coupling 2D coupling C-Coupler MASNUM-Wav POM 2D coupling 3-D coupling: Four choices for 1D interpolation for vertical level

  18. Example: model integration • Integrating a standalone model versions, e.g., CESM1.2.1, CESM1.0.5, WRF and MOM4p1, onto the C-Coupler platform • Several configuration files • Less than 10 lines of source code in the main driver • Enhancement for bitwise-identical reproducibility to the simulations

  19. Outline • C-Coupler development • C-Coupler1 • Bitwise identical reproducibility • Future work

  20. Reproducibility • A fundamental principle of scientific research • More and more claims for reproducibility of published results • Nature family, Science and Geoscientific Model Development, etc.

  21. Bitwise identical reproducibility? • It may be unnecessary, because climate simulations results are generally statistical characteristics of output data on time scales longer than a few months • It was extremely difficult to achieve bitwise identical reproducibility • The whole simulation setting needs to be recorded and recovered • Existing works show that climate simulation results can be sensitive to round-off error

  22. Experimental setups • Two fully coupled models: CESM1 and FGOALS-g2 • CMIP5 historical experiments: 60 years (1850-1909)

  23. Climatological mean TS by CESM1

  24. Climatological mean TS by FGOALS-g2 Bitwise identical reproducibility is important to Earth system modeling Current status of bitwise identical reproducibility of published results?

  25. Design of a survey: 17 journals

  26. Statistical characteristics of paper selection

  27. Results of the survey • No reply: 283 papers (80.6%) • No corresponding authors: 5 papers (1.4%) • Automatic email rejection: 66 papers (18.8%) • No active reply: 212 papers (60.4%) • Replied without required information: 54 papers (15.4%) • Replied without required information and confirmation: 7 papers (2%) • Inconvenient for reproduction: 47 papers (13.4%) • Unsuccessful re-run: 4 papers (1.1%) • Successful re-run: 5 papers (1.4%) • Successful bitwise identical reproduction: 5 papers (1.4%)

  28. Brief summary • Fellow scientists heavily depend on the authors’ help to reproduce the published simulation results • It is always inconvenient even impossible to recreate the same simulation setting as the whole simulation setting is rarely kept for a long time • The authors still have to spend a lot of efforts to help the fellow scientists who want to reproduce these results, even when the whole simulation setting can be recalled Bitwise identical reproducibility of Earth system modeling is currently at a very low level

  29. Reproducibility for model code Reproducibility for input data GIT server and code version id for each component model SVN server and version id for each input data file Code patch for each component model Check sum of each input data file Reproducibility for input parameters Reproducibility for parallel settings Script for generating the input parameter files of each component model Configuration file with the parallel settings of all component models Configure Reproducibility for computer system Reproducibility for Compiler and compiling options Name of the computer system Configuration file of compiling options of each component model C-Coupler platform Log information for configuring Username, computer name and configuration time, and error and warning report for configuration Information of compiler for each component model Experimental setup package for technical reproducibility Log files for technical reproducibility Output files for technical reproducibility Log files for compiling Name of model version Compile and run Description of model simulation Log files for the execution of model simulation Time of the corresponding configuration

  30. Flowchart for achieving bitwise identical reproducibility on the C-Coupler platform

  31. An example

  32. Worldwide standard of bitwise identical reproducibility • Any fellow scientists can independently obtain the whole simulation setting of published results and then can independently reproduce exactly the same simulation output • Requires scientists’ actions, journals’ actions, model intercomparison projects’ actions, and technical supports.

  33. A framework for achieving worldwide bitwise identical reproducibility

  34. Outline • C-Coupler development • C-Coupler1 • Bitwise identical reproducibility • Future work

  35. Future work • Coupling generator • Parallel optimization • Testing bed with benchmarks • ASCII configuration file format  XML format • More coupling functions

  36. Thank you

  37. Example: Computation performance Time for a data transfer (low resolution)

  38. Example: Computation performance Time for an interpolation (low resolution)

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