[issue44728] Testsuite fails on x86_64

[Mark Dickinson]

Mark Dickinson <dickinsm at 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?

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nosy: +mark.dickinson

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