>>>>> "Ranier" == Ranier Vilela <ranier...@gmail.com> writes:
Ranier> Hi, Ranier> Latest HEAD, fails with windows regress tests. Ranier> three | f1 | sqrt_f1 Ranier> -------+----------------------+----------------------- Ranier> | 1004.3 | 31.6906926399535 Ranier> - | 1.2345678901234e+200 | 1.11111110611109e+100 Ranier> + | 1.2345678901234e+200 | 1.11111110611108e+100 Ranier> | 1.2345678901234e-200 | 1.11111110611109e-100 Ranier> (3 rows) This error is a surprisingly large one. Normally one expects sqrt to be accurate to within half an ulp, i.e. accurate to the limits of the format, though the regression test avoids actually making this assumption. But in this case the true output we expect is: 1.111111106111085536...e+100 for which the closest representable float8 is 1.111111106111085583...e+100 (= 0x1.451DCD2E3ACAFp+332) which should round (since we're doing this test with extra_float_digits=0) to 1.11111110611109e+100 The nearest value that would round to 1.11111110611108e+100 would be 1.1111111061110848e+100 (= 0x1.451DCD2E3ACABp+332), which is a difference of not less than 4 ulps from the expected value. -- Andrew (irc:RhodiumToad)
