Enhancement for bitwise identical reproducibility of Earth system modeling on the C-Coupler platform

Ping, Li; Li, R.; Zhang, Chendi; Yang, Guangwen; Wang, Bochong; Dong, Lijun

doi:10.5194/gmdd-8-2403-2015

Cited by 9 publications

(8 citation statements)

References 20 publications

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“…First a bilinear interpolation is carried out on the two horizontal levels, followed by a vertical interpolation. Bitwise reproducibility of the simulation results has been verified [ Liu et al ., ].…”

Section: Model Descriptionsmentioning

confidence: 99%

Sensitivity of typhoon modeling to surface waves and rainfall

et al. 2017

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Improving intensity simulation and forecast of tropical cyclones has always been a challenge, although in recent years the track forecasts have been remarkably improved. In this study, we explore the sensitivity of typhoon simulation to three physical processes using a fully coupled atmosphere‐ocean‐wave model. Two storms, a strong and a weak one, have been chosen. The effects of wave breaking induced sea spray, ocean vertical mixing associated with nonbreaking surface waves, and sea surface cooling due to intense rainfall are assessed by means of a set of numerical experiments. The results show and confirm that sea spray leads to an increase of typhoon intensity by enhancing the air‐sea heat flux, while nonbreaking wave‐induced vertical mixing and rainfall lead to a decrease. Each process can be relevant, depending on wind and wave conditions. These can vary dramatically when typhoons interact with not sufficiently well‐defined coastal areas, typically an archipelago. Compared with the control runs, when all the three physical processes are considered, the (absolute) difference between the modeled sea level pressure and best track data is reduced from 26.05 to 0.70 hPa for typhoon Haiyan, and from −9.42 to −8.67 hPa for typhoon Jebi. We have found a steady overestimate of the dimensions of the typhoons. We have verified an extreme sensitivity to the initial conditions, especially when small differences in the typhoon track may imply different relevance of the physical processes, like the ones we have considered, governing the evolution of the storm.

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Section: Model Descriptionsmentioning

confidence: 99%

Sensitivity of typhoon modeling to surface waves and rainfall

et al. 2017

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“…Song et al (2012) and Hong et al (2013) investigated the uncertainty due to the round-off error in climate simulations. Liu et al (2015a, b) discussed the importance of bitwise identical reproducibility in climate models.…”

Section: Introductionmentioning

confidence: 99%

Machine dependence and reproducibility for coupled climate simulations: the HadGEM3-GC3.1 CMIP Preindustrial simulation

et al. 2020

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Abstract. When the same weather or climate simulation is run on different high-performance computing (HPC) platforms, model outputs may not be identical for a given initial condition. While the role of HPC platforms in delivering better climate projections is to some extent discussed in the literature, attention is mainly focused on scalability and performance rather than on the impact of machine-dependent processes on the numerical solution. Here we investigate the behaviour of the Preindustrial (PI) simulation prepared by the UK Met Office for the forthcoming CMIP6 (Coupled Model Intercomparison Project Phase 6) under different computing environments. Discrepancies between the means of key climate variables were analysed at different timescales, from decadal to centennial. We found that for the two simulations to be statistically indistinguishable, a 200-year averaging period must be used for the analysis of the results. Thus, constant-forcing climate simulations using the HadGEM3-GC3.1 model are reproducible on different HPC platforms provided that a sufficiently long duration of simulation is used. In regions where El Niño–Southern Oscillation (ENSO) teleconnection patterns were detected, we found large sea surface temperature and sea ice concentration differences on centennial timescales. This indicates that a 100-year constant-forcing climate simulation may not be long enough to adequately capture the internal variability of the HadGEM3-GC3.1 model, despite this being the minimum simulation length recommended by CMIP6 protocols for many MIP (Model Intercomparison Project) experiments. On the basis of our findings, we recommend a minimum simulation length of 200 years whenever possible.

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“…One may think it is easy to update compiling setups, just by installing new compiler version or changing compiler flags. However, it is challenging to update compiling setups for Earth system modeling, because researchers may get significantly different results from the same experiment when using different compiling setups (Liu et al, 2015b). A compiler not only translates the code in a high-level programming language to a low-level language but also tries to improve computational performance of the codes with compiler optimization schemes.…”

Section: Introductionmentioning

confidence: 99%

“…The first challenge concerns reproducibility of simulation results. Due to the chaotic nature of the climate system, more and more studies have shown that trivial round-off errors can trigger significant changes in simulation results of Earth system modeling (Hong et al, 2013;Liu et al, 2015b;Song et al, 2012). Due to the differences of performance optimization schemes among different compiling setups, a change of compiling setups potentially introduces round-off errors.…”

Section: Introductionmentioning

confidence: 99%

“…There are already efforts for the abovementioned issues. It has been demonstrated that with a certain compiler flag, different compiler versions can achieve bitwise identical simulation results for a given model (Liu et al, 2015a). But it is still not known whether compiling setups with the same compiler version but different compiler flags can achieve bitwise identical simulation results.…”

Section: Introductionmentioning

confidence: 99%

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Bitwise identical compiling setup: prospective for reproducibility and reliability of Earth system modeling

Ping

Yang

et al. 2016

Geosci. Model Dev.

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Reproducibility and reliability are fundamental principles of scientific research. A compiling setup that includes a specific compiler version and compiler flags is an essential technical support for Earth system modeling. With the fast development of computer software and hardware, a compiling setup has to be updated frequently, which challenges the reproducibility and reliability of Earth system modeling. The existing results of a simulation using an original compiling setup may be irreproducible by a newer compiling setup because trivial round-off errors introduced by the change in compiling setup can potentially trigger significant changes in simulation results. Regarding the reliability, a compiler with millions of lines of code may have bugs that are easily overlooked due to the uncertainties or unknowns in Earth system modeling. To address these challenges, this study shows that different compiling setups can achieve exactly the same (bitwise identical) results in Earth system modeling, and a set of bitwise identical compiling setups of a model can be used across different compiler versions and different compiler flags. As a result, the original results can be more easily reproduced; for example, the original results with an older compiler version can be reproduced exactly with a newer compiler version. Moreover, this study shows that new test cases can be generated based on the differences of bitwise identical compiling setups between different models, which can help detect software bugs in the codes of models and compilers and finally improve the reliability of Earth system modeling.Published by Copernicus Publications on behalf of the European Geosciences Union.

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Enhancement for bitwise identical reproducibility of Earth system modeling on the C-Coupler platform

Cited by 9 publications

References 20 publications

Sensitivity of typhoon modeling to surface waves and rainfall

Sensitivity of typhoon modeling to surface waves and rainfall

Machine dependence and reproducibility for coupled climate simulations: the HadGEM3-GC3.1 CMIP Preindustrial simulation

Bitwise identical compiling setup: prospective for reproducibility and reliability of Earth system modeling

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