Division issue with 3.8.2 on AIX 7.1

[Terry Reedy]

On 6/3/2020 8:11 PM, Dennis Lee Bieber wrote:
> On Tue, 2 Jun 2020 12:26:16 -0500, Albert Chin
> <python-list at mlists.thewrittenword.com> declaimed the following:
> 
>> I've built Python 3.8.2 on AIX 5.2, 5.3, 6.1, and 7.1. I am seeing
>> different results for the following Python program:
>>   $ python3 -c "eps = 2.0 ** -53.0; tiny = 2.0 ** -1022.0; \
>> print ((1.0 - eps) / tiny * 4.0)"
>>
>> I get the correct result, 1.7976931348623157e+308, on AIX 5.2, 5.3,
>> and 6.1. But, on 7.1, I get "inf".

Execute "print(1.0-eps, tiny)" and see if they differ.

>> Anyone know where can I look in the Python source code to investigate
>> this?
> 
> 	Have you considered that it might be something in an underlying C
> library (especially for the double-precision exponentiation)?

This is a more likely source of the change than our code.

-- 
Terry Jan Reedy