Mark Dickinson <dicki...@gmail.com> added the comment:

Extract from the log - from the configure output:

> checking for expm1... yes

and from the test output

> expm10118: expm1(27.0): expected 532048240600.79865, got 532048240600.7976 
> (error = 0.00104 (17 ulps); permitted error = 0 or 5 ulps)
> expm10119: expm1(123.0): expected 2.6195173187490626e+53, got 
> 2.619517318749054e+53 (error = 8.51e+38 (20 ulps); permitted error = 0 or 5 
> ulps)
> expm10300: expm1(300.0): expected 1.9424263952412558e+130, got 
> 1.942426395241274e+130 (error = 1.82e+116 (74 ulps); permitted error = 0 or 5 
> ulps)
> expm10301: expm1(700.0): expected 1.0142320547350045e+304, got 
> 1.0142320547349733e+304 (error = 3.12e+290 (256 ulps); permitted error = 0 or 
> 5 ulps)
> expm10307: expm1(709.5): expected 1.3549863193146328e+308, got 
> 1.354986319314675e+308 (error = 4.21e+294 (211 ulps); permitted error = 0 or 
> 5 ulps)

The first part indicates that your math library does provide expm1, so Python 
goes ahead and uses it. The errors from test_math show that the expm1 
implementation provided by your math library has accuracy problems for large 
inputs. From the other failures, I suspect that the underlying issue is 
actually an issue with exp (but our tests for exp are not so thorough as those 
for expm1).

In short, the tests represent issues with the underlying C math library. What 
OS is this, and who supplies the libm?

----------
nosy: +mark.dickinson

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<https://bugs.python.org/issue44728>
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