[GitHub] asmushetzel opened a new pull request #11035: added more detailed error messages for potri/potrf

[GitBox <gi...@apache.org>]

asmushetzel opened a new pull request #11035: added more detailed error messages for potri/potrf
URL: https://github.com/apache/incubator-mxnet/pull/11035
 
 
   ## Description ##
   Added more detailed error messages for potrf/potri as a response to #10964
   We check a lot of conditions upfront, but don't check conditions that are too complex and would actually require writing a complex algorithm just for checking. For potrf, this is whether the input matrix is symmetric and positive definite, for potri this is whether the input matrix is indeed the output of a prior potrf-computation. To help the user in case of an error, we repeat these two unchecked preconditions on the input when displaying the error message. 
   
   There is a limit when we can provide such more useful messages. All cblas-routines do not return any error code (on CPU), so we can realistically cover only lapack routines (which are also the ones that have most complex preconditions). Getting the same type of more elaborate error messages on Cuda is also difficult, specifically as potri on GPU has to be implemented based on blas-routines and not as a single function call. 
   
   As a compromise, we will initially supply such advanced messages for the most common use cases only: potrf/potri on CPU. 
   
   
    
   ## Checklist ##
   ### Essentials ###
   Please feel free to remove inapplicable items for your PR.
   - [X] Changes are complete (i.e. I finished coding on this PR)
   - [ X] To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change
   

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