Revision as of 14:09, 30 May 2022 view source Chris Huxley (talk \| contribs) Bureaucrats, Administrators 7,776 edits →I am running existing and developed case and see differences away from the model changes. Why? ← Older edit		Revision as of 10:30, 4 August 2022 view source Pavlina Monhartova (talk \| contribs) Bureaucrats, Administrators 5,372 edits →Why seemingly identical models can produce non-identical results? Newer edit →
Line 54: =Why seemingly identical models can produce non-identical results?= Generally speaking single path numerical solvers such as those used for hydraulic modelling should be able to produce the same numerical results twice to the last bit of every binary number calculated and output. However, this can become difficult with parallel computations as the order in which a list of single or double precision numbers are summated can produce slightly different rounding errors and thereby produce very slightly different results. For the vast majority of models TUFLOW Classic~~, TUFLOW HPC~~ and TUFLOW FVHPC will reproduce numerically identical results when run on the same CPU/GPU. Occasionally this might not be the case when identical simulations are run on different CPUs/GPUs due to hardware differences.<br> Prior to 2020-10-AB release, the new boundary method introduced in TUFLOW HPC 2020-01-AA release for inflowing HT and QT boundaries (refer see Section 6.1 of the 2020 Release Notes) can in rare situations be affected by bitwise reproducibility when parallelised. When this issue occurs, very slight numerical differences can occur throughout the model, noting that they will be of a much smaller magnitude than those that occur when carrying out impact assessments, but will cause undesirable numerical noise in the impact mapping.<br>

Modelling Accuracy Uncertainties Impact Mapping: Difference between revisions