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FAQ: Testing and Validation

This section is intended to address issues you might encounter when testing or validating a model after porting to HECToR.

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Q. I get different answers on the two systems when validating my code. What can I do to find out the cause of the problem?

A. It is unrealistic to expect two different systems to give identical answers for large, complex scientific computations. Small differences can arise from the different order in which operations are performed due to the different optimisations performed. If, however, the differences are significant, the following can help to identify the source:

  • Ensure all code, datafiles and libraries used are identical or the same version.
  • Reduce the level of optimisation used, then increase back to the desired level in groups to find the key parts of the code which are associated with the problem.
  • Simplify the problem to identify a key feature/section associated with the differences.

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