[issue34376] Improve accuracy of math.hypot() and math.dist()

[Raymond Hettinger]

Raymond Hettinger <raymond.hettinger at gmail.com> added the comment:

Retested using Tim's ulp(x) function (see attached script).  The accuracy results are for 1,000 trials using 10,000 arguments to hypot() where the arguments are generated using triangular(0.999, 1.001) and arranged in the least favorable order, largest-to-smallest:

Patched:  
[(-1.0, 129),
 (0.0, 723),
 (1.0, 148)]

Baseline:
[(-33.0, 2),
 (-32.0, 1),
 (-31.0, 1),
 (-28.0, 5),
 (-27.0, 2),
 (-26.0, 4),
 (-25.0, 3),
 (-24.0, 4),
 (-23.0, 1),
 (-21.0, 9),
 (-20.0, 7),
 (-19.0, 6),
 (-18.0, 15),
 (-17.0, 12),
 (-16.0, 6),
 (-15.0, 12),
 (-14.0, 14),
 (-13.0, 15),
 (-12.0, 15),
 (-11.0, 25),
 (-10.0, 21),
 (-9.0, 24),
 (-8.0, 26),
 (-7.0, 29),
 (-6.0, 36),
 (-5.0, 33),
 (-4.0, 37),
 (-3.0, 31),
 (-2.0, 39),
 (-1.0, 43),
 (0.0, 48),
 (1.0, 45),
 (2.0, 32),
 (3.0, 37),
 (4.0, 34),
 (5.0, 25),
 (6.0, 36),
 (7.0, 29),
 (8.0, 35),
 (9.0, 27),
 (10.0, 24),
 (11.0, 17),
 (12.0, 18),
 (13.0, 18),
 (14.0, 18),
 (15.0, 11),
 (16.0, 8),
 (17.0, 6),
 (18.0, 9),
 (19.0, 15),
 (20.0, 8),
 (21.0, 5),
 (22.0, 6),
 (23.0, 4),
 (24.0, 2),
 (25.0, 1),
 (28.0, 2),
 (30.0, 1),
 (33.0, 1)]

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Added file: https://bugs.python.org/file47746/hypot_accuracy.py

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<https://bugs.python.org/issue34376>
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