The changes in this beta will be available in the upcoming 4.9 production release that will be , due out at the end of June 2019.We have fixed different results on different machines! We'll discuss in further detail improvements for plugins,
Highlights of this release include fixing the problem of different machines giving different results (for two models), a 'removal' script for plugins and improvements to the Map tool and the Lascam plugin. This beta
Beta 4.8.3 also has improvements to:
- recorder sets,
- editing constituent models,
- ownership recorders in weirs and off allocation,
- saved run information in the Results Manager,
- validation of supply point options, and
- orders are now redistributed at extraction time for use debit accounts.
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Firstly, the problem of different results on different machines
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has been fixed!
Technical Details:
Source uses the Microsoft .NET framework, the problem was caused by 2 functions in the System.Math library. Both System.Math.Pow() and System.Math.Exp() can give different results for some number combinations on different machines. For individual function calls, different results occurred at 0.09% of the time with our randomly generated test data. We believe the issue is from different CPU’s implementing different optimisations to perform the operations as efficiently as possible. The functions are not implemented directly within the Microsoft .NET framework, instead, they are implemented in the Microsoft C run-time libraries which are used by the .NET framework, as well as by a number of other languages including C++. So the nature of the .NET framework, which is an interpreted language, wasn’t part of the issue and the same results would have been obtained if implemented in C++. We have since tested all available System.Math functions and these are the only two we have found that can produce different results on different machines. The vast majority of models don’t see the issue since the differences are very minor and for an individual operation, the difference is only at the last decimal place. However, for very large models with lots of feedback in the model, when the issue occurs it can snowball into meaningful result differences.
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Plugins that need persistence can now include a removal script so plugins can remove themselves from a project when they are not needed any more or have been added accidentally. There is an example provided in the Example Node model plugin.
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