[Numpy-discussion] Change in scalar upcasting rules for 1.6.x?

Travis Oliphant travis@continuum...
Tue Feb 14 00:07:34 CST 2012

> >
> > No argument on any of this.   It's just that this needs to happen at NumPy 2.0, not in the NumPy 1.X series.   I think requiring a re-compile is far-less onerous than changing the type-coercion subtly in a 1.5 to 1.6 release.      That's my major point, and I'm surprised others are more cavalier about this. 
> I thought the whole datetime debacle was the impetus for binary compatibility? Also, I disagree with your "cavalier" charge here.  When we looked at the rationale for the changes Mark made, the old behavior was not documented, broke commutibility, and was unexpected.  So, if it walks like a duck...
> Now we are in an odd situation. We have undocumented old behavior, and documented new behavior.  What do we do?  I understand the drive to revert, but I hate the idea of putting back what I see as buggy, especially when new software may fail with old behavior.
> Maybe a Boolean switch defaulting to new behavior?  Anybody having issues with old software could just flip the switch?
> I think we just leave it as is. If it was a big problem we would have heard screams of complaint long ago. The post that started this off wasn't even a complaint, more of a "see this". Spending time reverting or whatever would be a waste of resources, IMHO.
> Chuck 

You might be right, Chuck.   I would like to investigate more, however. 

What I fear is that there are *a lot* of users still on NumPy 1.3 and NumPy 1.5.   The fact that we haven't heard any complaints, yet, does not mean to me that we aren't creating headache for people later who have just not had time to try things.  

However, I can believe that the specifics of "minor" casting rules are probably not relied upon by a lot of codes out there.   Still, as Robert Kern often reminds us well --- our intuitions about this are usually not worth much. 

I may be making more of this then it's worth, I realize.   I was just sensitive to it at the time things were changing (even though I didn't have time to be vocal), and now hearing this users experience, it confirms my bias...  Believe me, I do not want to "revert" if at all possible.    There is plenty of more work to do, and I'm very much in favor of the spirit of the work Mark was and is doing. 

Best regards,


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