HPC Introduction: Difference between revisions
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=Introduction=
As of TUFLOW build 2017-09-AA, TUFLOW offers HPC (Heavily Parallelised Compute) as an alternate 2D Shallow Water Equation (SWE) solver to TUFLOW Classic. Whereas TUFLOW Classic is limited to running a simulation on a single CPU core, HPC provides parallelisation of the TUFLOW model allowing modellers to run a single TUFLOW model across multiple CPU cores or GPU graphics cards (which utilise thousands of smaller CUDA* cores). Simulations using GPU hardwareshown to provide significantly quicker model run times for TUFLOW users.<br>
In general most of the functionality and features of TUFLOW Classic are available in HPC, with more of these features becoming available to HPC in due time. To find out more about what TUFLOW Classic features aren’t included in the latest TUFLOW HPC build you can reference the <u>[[HPC Features | HPC Features Wiki Page]]</u> or the <u>[https://tuflow.com/Download/TUFLOW/Releases/2017-09/TUFLOW%20Release%20Notes.2017-09.pdf TUFLOW 2017-09 Release Notes]</u>. <br>
===Solution Scheme and Parallelisation===
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===Mass Conservation and Timestep===
The explicit finite volume solution scheme utilised in HPC is mass conserving by construction. This differs to TUFLOW Classic, which can continue to simulate a model with some volume error due to it being an implicit finite difference scheme. The stability of the explicit finite volume scheme used in TUFLOW HPC is linked to the time step, flow velocities, water depth, and eddy viscosity. The maximum timestep that can be used while maintaining model stability changes as the model evolves. While it is possible to choose a fixed timestep ahead of time (similarly to TUFLOW Classic), shorter run times and guaranteed model stability from start to finish may be achieved through the use of adaptive time stepping where the solver continually modifies the timestep based on various stability criteria. This is explained in more detail in our <u>[[Adaptive_Timestepping |HPC Adaptive Timestep Wiki Page]]</u>.<br>
===Cell Discretisation===
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===Benefits of HPC===
So what does this mean for modellers? By providing the ability to run models on Graphics Cards or across multiple CPU cores, we can achieve significantly shorter model run times, increasing our modelling capabilities to be able to run continuous hydraulic models, with increased cell resolution, across larger extents and more scenarios (Monte Carlo, rainfall ensembles). If you would like to learn more about HPC’s run times and modelling benefits then please refer to our <u>[[Hardware Benchmarking | Hardware Benchmarking Wiki Page]]</u>. <br>
∗ Cuda Cores are patented to Nvidia graphics cards. This means that TUFLOW is limited to running on CUDA enabled graphics cards only.<br>
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