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bpo-33089: Multidimensional math.hypot() #8474

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Merged
rhettinger merged 21 commits into from
Jul 28, 2018
Merged

bpo-33089: Multidimensional math.hypot() #8474

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ec15283
Segfaulting rough draft without NaN support or raising Overflow
rhettinger Jul 7, 2018
abce2b0
Working verion. Double pass over input tuple. No inf/nan handling.
rhettinger Jul 7, 2018
241932e
Simplify. Remove unnecessary second error check. Remove n<=1 special …
rhettinger Jul 7, 2018
51c52fc
Add some tests
rhettinger Jul 24, 2018
de3c16b
Add support for special values.
rhettinger Jul 25, 2018
18babd4
Test scaling for large values
rhettinger Jul 25, 2018
6c412d2
Add tests for small values
rhettinger Jul 26, 2018
780024b
Neaten-up test cases
rhettinger Jul 26, 2018
d82df99
Use module level constants for float min/max
rhettinger Jul 26, 2018
1a32ac7
Expand range for large value tests
rhettinger Jul 26, 2018
82a12e5
Improve variable name
rhettinger Jul 26, 2018
2d2e3aa
Replace the existing hypot() code
rhettinger Jul 26, 2018
6edd323
Clean stray whitespace
rhettinger Jul 26, 2018
9c25c65
Write the docstring
rhettinger Jul 26, 2018
c4dfbe5
Update the main documentation
rhettinger Jul 26, 2018
0734edd
Add blurb
rhettinger Jul 26, 2018
43471a9
Address Tim's review comments.
rhettinger Jul 27, 2018
3818324
Update argument clinic checksum
rhettinger Jul 27, 2018
8298444
Reuse converted floats rather than converting twice
rhettinger Jul 27, 2018
d785025
Add test for a negative zero input
rhettinger Jul 28, 2018
ee1374c
Test for failed malloc(). Only test inf at the end.
rhettinger Jul 28, 2018
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Neaten-up test cases
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@rhettinger
rhettinger committed Jul 26, 2018
commit 780024b7314752b54c8532b7425a0b05563102c8
40 changes: 24 additions & 16 deletions Lib/test/test_math.py
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Original file line number Diff line number Diff line change
Expand Up @@ -732,29 +732,36 @@ def testHypot(self):
self.assertTrue(math.isnan(math.hypot(NAN, -2.0)))

def test_multi_hypot(self):
from decimal import Decimal as D
from decimal import Decimal
from fractions import Fraction

hypot = math.mh

self.assertEqual(hypot(12.0, 5.0), 13.0) # Float inputs. Exact output.
self.assertEqual(hypot(12, 5), 13) # Int inputs
self.assertEqual(hypot(D(12), D(5)), 13) # Decimal inputs

self.assertEqual(hypot(0.0, 0.0), 0.0) # Max input is zero
self.assertEqual(hypot(-10.5), 10.5) # Negative input

with self.assertRaises(TypeError):
hypot(x=1) # Reject keyword args

# Test 0 to 4 dimensional inputs
args = math.e, math.pi, math.sqrt(2.0), math.gamma(3.5)
# Test different numbers of arguments from zero to five
args = math.e, math.pi, math.sqrt(2.0), math.gamma(3.5), math.sin(2.1)
for i in range(len(args)+1):
self.assertAlmostEqual(
hypot(*args[:i]),
math.sqrt(sum(s**2 for s in args[:i]))
)

# Test special values.
# Test allowable types (those with __float__)
self.assertEqual(hypot(12.0, 5.0), 13.0)
self.assertEqual(hypot(12, 5), 13)
self.assertEqual(hypot(Decimal(12), Decimal(5)), 13)
self.assertEqual(hypot(Fraction(12, 32), Fraction(5, 32)), Fraction(13, 32))
self.assertEqual(hypot(bool(1), bool(0), bool(1), bool(1)), math.sqrt(3))

# Test corner cases
self.assertEqual(hypot(0.0, 0.0), 0.0) # Max input is zero
self.assertEqual(hypot(-10.5), 10.5) # Negative input

@tim-one tim-one Jul 26, 2018

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Add self.assertEqual(hypot(), 0.0)?

@rhettinger rhettinger Jul 27, 2018

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Okay, added an explict test for this case. FWIW, this was already tested in the section "Test different numbers of arguments (from zero to five)".


# Test handling of bad arguments
with self.assertRaises(TypeError): # Reject keyword args
hypot(x=1)
with self.assertRaises(TypeError): # Reject values without __float__
hypot(1.1, 'string', 2.2)

# Any infinity gives positive infinity.
self.assertEqual(hypot(INF), INF)
self.assertEqual(hypot(0, INF), INF)
Expand All @@ -764,6 +771,7 @@ def test_multi_hypot(self):
self.assertEqual(hypot(-INF, INF), INF)
self.assertEqual(hypot(-INF, -INF), INF)
self.assertEqual(hypot(10, -INF), INF)

# If no infinity, any NaN gives a Nan.
self.assertTrue(math.isnan(hypot(NAN)))
self.assertTrue(math.isnan(hypot(0, NAN)))
Expand All @@ -775,12 +783,12 @@ def test_multi_hypot(self):
halfmax = sys.float_info.max / 2.0
for n in range(10):
self.assertEqual(hypot(*([halfmax]*n)), halfmax * math.sqrt(n))

# Verify scaling for extremely small values
small = sys.float_info.min
a, b, c = 5, 12, 13
for exp in range(32):
scale = small / 2 ** exp
self.assertEqual(math.hypot(a*scale, b*scale), c*scale)
self.assertEqual(math.hypot(12*scale, 5*scale), 13*scale)

@tim-one tim-one Jul 26, 2018 •
edited
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This makes me nervous, because it depends on that

12 * math.sqrt(1 + (5/12)**2)

happens to be exactly 13.0 despite that 5/12 isn't exactly representable. Would be happier with:

self.assertEqual(math.hypot(4*scale, 3*scale), 5*scale)

because every intermediate value in

4 * math.sqrt(1 + (3/4)**2)

is exactly representable in binary.

@rhettinger rhettinger Jul 27, 2018

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Okay, changed to a 3-4-5 triangle.


def testLdexp(self):
self.assertRaises(TypeError, math.ldexp)
Expand Down