HPC FAQ: Difference between revisions
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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.
= I have been given a model developed in an older release and the results are different in a newer release. Why? =
If comparing a Classic model with HPC, check the first question [[HPC_FAQ#Will_TUFLOW_HPC_and_TUFLOW_Classic_results_match.3F | Will TUFLOW HPC and TUFLOW Classic results match?]] <br>
In addition to above, there are numerous reasons why model results would be different between different TUFLOW releases, Classic or HPC regardless:
* General improvements
* Some new functionality can cause a significant change in results. For example, Sub-Grid Sampling (SGS) where a model uses a too coarse cell resolution in high flow areas of highly variable topography (relative to the 2D cell size). SGS will greatly improve the model's ability to convey water accurately in this situation with vastly improved results convergence due to varying the cell size compared to not using SGS. Another example is the new default sub-grid turbulence scheme in the 2020 release of TUFLOW HPC that is cell size independent and allows modellers to use cell sizes much smaller than the depth across all scales from flume to large rivers.
* New features that use GIS attributes previously reserved and unused. If these attributes were not populated with the recommended “reserved” value (usually 0 or blank), then they can cause unpredictable results in later releases.▼
*
▲* New features that use GIS attributes previously reserved
* Bug fixes noting that most bug fixes are input/output related and rarely affect the model's results.
Generally, there should not be substantial differences as the fundamental equations being solved are unchanged. If significant differences (>10% of depth change across the whole model) are observed then it’s most likely due to the last couple of dot points above. To identify the cause(s) for the change, the model can be run with the latest build for each release to identify in which release(s) the significant changes occurred. The changes for each release are documented in their release notes. Past releases and release notes are all available [https://www.tuflow.com/Tuflow%20Previous%20Release.aspx. here].<br>▼
The recommendation is usually for new or reworked models to use the newest build to take advantage of the latest features and enhancements. However, particularly if a model is calibrated, using old builds of TUFLOW or winding back default settings using “Defaults ==” is reasonable for established models.<br>▼
▲Generally, there should not be substantial differences as the fundamental equations being solved are unchanged and TUFLOW Classic and HPC solvers have always solved all the physical terms using a 2nd order spatial approach. If significant differences (>10% of depth change across the whole model) are observed then it’s most likely due to the
The changes for each release are documented in their release notes. Past releases and release notes are all available [https://www.tuflow.com/downloads/tuflow-classichpc-archive/. here].<br>
▲The recommendation is usually for new or reworked models to use the newest build to take advantage of the latest features and enhancements. However, particularly if a model is calibrated, using
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