1 | | == Modelling Model Performance == |
| 1 | = Performance Modelling = |
| 2 | |
| 3 | As we move towards the exascale-era, HPC systems are becoming increasingly complex with, for example, co-processors (eg, GPUs, Intel Xeon Phis), Non-uniform memory-access (NUMA) nodes, and various network structures, as well as the trend for increasing numbers of cores with decreasing speeds and decreasing memory per core. This makes it challenging to predict the performance of real applications on new and forthcoming machines. |
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| 5 | Similarly scientific software is evolving in order to solve larger and more intricate problems, which involves exploring more scalable model formulations, numerical methods and algorithms. An example of this is the joint Met Office and NERC project, Gung-Ho!, to develop the next generation Unified Model weather and climate prediction system: http://collab.metoffice.gov.uk/twiki/bin/view/Project/NGWCP |
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| 7 | '''Therefore, we want to know how current and future models will perform on current and emerging systems, in terms of time-to-solution, resource efficiency and problem scalability. Performance modelling can be used as a tool to explore answers to these questions.''' |
| 8 | |
| 9 | In this case a performance model encapsulates information about the software and hardware to make a prediction of elapsed wallclock run time for a given scenario. |
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| 11 | == Unified Model == |
| 12 | |
| 13 | We looked at the performance of a HadGEM3 configuration at UM 7.3 for N96 and N216 global problem sizes. At the time this work was carried out, there was concern that the UM new dynamics would be limited in it's ability to scale to very high resolution global grids (see for example: http://research.metoffice.gov.uk/research/nwp/publications/mosac/doc-2009-10.pdf) |
| 14 | |
| 15 | We explored: |
| 16 | * How the computational and communication performance of different parts of the model scaled with core count and resolution. |
| 17 | * How the time to complete a timestep varied over a 3 day run. |
| 18 | * How the number of solver iterations required to converge changed with resolution. |
| 19 | |
| 20 | This information was also used to outline an analytical application performance model for the UM configuration. |
| 21 | |
| 22 | Poster: |
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| 24 | == Shallow water model == |