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I'd be very curious to know if there is any impact to choosing Numpy C ordered arrays or Fortran ordered arrays. As a long time Matlab user (since 1993) who moved to Python 3 years ago, I have always defaulted to Fortran order because it was what I was used to and seemed more intuitive. I did play with C ordered arrays but didn't find an advantage in my limited investigation.

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There may still be a few routines that expect C-ordered arrays and so require a copy be made when given a Fortran-ordered array --- especially as you extend to one of libraries that use NumPy. For the most, part, however, Fortran-ordered arrays should work well. It all comes down to the expectation of the routine writer.

I think it depends on whether an algorithm is forced to traverse an array in the cache-efficient direction or not. Oftentimes you can't choose whether to make your outer loop rows or columns so the performance could go either way.

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