Revision as of 15:51, 1 February 2021 view source Pavlina Monhartova (talk \| contribs) Bureaucrats, Administrators 5,343 edits →My HPC model uses double precision due to unstable 1D channel. How can I make it stable in single precision? ← Older edit		Revision as of 14:24, 3 February 2021 view source Pavlina Monhartova (talk \| contribs) Bureaucrats, Administrators 5,343 edits No edit summary Newer edit →
Line 59: = How much faster is TUFLOW HPC compared to Classic? = This is largely based on hardware that is used to run HPC models (CPU and GPU) and its performance. On average, HPC using GPU hardware runs about 10 to 20 times faster than Classic and about 30 to 40 times faster than HPC using the default number of CPU threads. Even though HPC using CPU hardware is with default settings slower than Classic, more CPU threads can be used to achieve faster run times. As TUFLOW Classic is not parallelised it can only run on one CPU thread and the runtime cannot be further improved with more CPU resources.<br> For further information and discussion see: <u>[[Hardware_Benchmarking_Topic_HPC_on_CPU_vs_GPU \| Hardware Benchmarking Topic HPC on CPU vs GPU]]</u>.<br> <br> Line 72: <font color="blue"><tt>Viscosity Coefficients</tt></font> <font color="red"><tt>==</tt></font><tt> 0.5, 0.05</tt> <br> Not all HPC models will show an increase in run time when changing from the 2018 to the 2020 release. Models that are controlled by the wave celerity or Courant control numbers and not the diffusion control number are likely to be similar in runtime. Some models will be even faster with the last 2020 release due to other improvements. However, especially where the cell size is smaller than the depth, the Wu approach is vastly superior to the Smagorinsky, and the more sophisticated Wu solution may start causing the <u>[[HPC_Adaptive_Timestepping \| diffusion control number]]</u> to control the timestepping causing longer run times.<br> Despite the possible increase in runtime for some models, the Wu turbulence scheme is warranted particularly as cell sizes are typically getting smaller.<br> <br> Line 92: The below suggestions can be implemented to eliminate the instability and/or the decrease in control numbers: * Specify initial water level for the whole model with <font color="blue"><tt>Set IWL</tt></font> command or locally with <font color="blue"><tt>Read GIS IWL</tt></font> command. The wet cells can limit the adaptive timestep through the <u>[[HPC_Adaptive_Timestepping#HPC_2D_Timestep \| Shallow Wave Celerity Number]]</u>, and prevent the HPC solver from using big timesteps. * Use <font color="blue"><tt>Timestep Maximum</tt></font> command to cap the maximum timestep to not get too high. <br>

HPC FAQ: Difference between revisions