HPC FAQ: Difference between revisions
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= Why is my model using 2020 HPC twice as slow as 2018 HPC?=
The change in runtime can be due to different timestepping applied with the new default - mesh size insensitive turbulence model - Wu instead of Smagorinsky. To confirm this is the case, test run your model with 2020release and the following commands:<br>
<font color="blue"><tt>Viscosity Formulation </tt></font> <font color="red"><tt>==</tt></font><tt> Smagorinsky</tt> <br>
<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 runtime when changing from the 2018 to the 2020 release - models that are controlled by the wave celerity or velocity 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.
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