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Use subTest() in math.fma() tests #131125

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Mar 12, 2025
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Use subTest() in math.fma() tests #131125

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137 changes: 73 additions & 64 deletions Lib/test/test_math.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2693,9 +2693,10 @@ def test_fma_nan_results(self):

# If any input is a NaN, the result should be a NaN, too.
for a, b in itertools.product(values, repeat=2):
self.assertIsNaN(math.fma(math.nan, a, b))
self.assertIsNaN(math.fma(a, math.nan, b))
self.assertIsNaN(math.fma(a, b, math.nan))
with self.subTest(a=a, b=b):
self.assertIsNaN(math.fma(math.nan, a, b))
self.assertIsNaN(math.fma(a, math.nan, b))
self.assertIsNaN(math.fma(a, b, math.nan))

def test_fma_infinities(self):
# Cases involving infinite inputs or results.
Expand All @@ -2707,57 +2708,62 @@ def test_fma_infinities(self):
for c in non_nans:
for infinity in [math.inf, -math.inf]:
for zero in [0.0, -0.0]:
with self.assertRaises(ValueError):
math.fma(infinity, zero, c)
with self.assertRaises(ValueError):
math.fma(zero, infinity, c)
with self.subTest(c=c, infinity=infinity, zero=zero):
with self.assertRaises(ValueError):
math.fma(infinity, zero, c)
with self.assertRaises(ValueError):
math.fma(zero, infinity, c)

# ValueError when a*b and c both infinite of opposite signs.
for b in positives:
with self.assertRaises(ValueError):
math.fma(math.inf, b, -math.inf)
with self.assertRaises(ValueError):
math.fma(math.inf, -b, math.inf)
with self.assertRaises(ValueError):
math.fma(-math.inf, -b, -math.inf)
with self.assertRaises(ValueError):
math.fma(-math.inf, b, math.inf)
with self.assertRaises(ValueError):
math.fma(b, math.inf, -math.inf)
with self.assertRaises(ValueError):
math.fma(-b, math.inf, math.inf)
with self.assertRaises(ValueError):
math.fma(-b, -math.inf, -math.inf)
with self.assertRaises(ValueError):
math.fma(b, -math.inf, math.inf)
with self.subTest(b=b):
with self.assertRaises(ValueError):
math.fma(math.inf, b, -math.inf)
with self.assertRaises(ValueError):
math.fma(math.inf, -b, math.inf)
with self.assertRaises(ValueError):
math.fma(-math.inf, -b, -math.inf)
with self.assertRaises(ValueError):
math.fma(-math.inf, b, math.inf)
with self.assertRaises(ValueError):
math.fma(b, math.inf, -math.inf)
with self.assertRaises(ValueError):
math.fma(-b, math.inf, math.inf)
with self.assertRaises(ValueError):
math.fma(-b, -math.inf, -math.inf)
with self.assertRaises(ValueError):
math.fma(b, -math.inf, math.inf)

# Infinite result when a*b and c both infinite of the same sign.
for b in positives:
self.assertEqual(math.fma(math.inf, b, math.inf), math.inf)
self.assertEqual(math.fma(math.inf, -b, -math.inf), -math.inf)
self.assertEqual(math.fma(-math.inf, -b, math.inf), math.inf)
self.assertEqual(math.fma(-math.inf, b, -math.inf), -math.inf)
self.assertEqual(math.fma(b, math.inf, math.inf), math.inf)
self.assertEqual(math.fma(-b, math.inf, -math.inf), -math.inf)
self.assertEqual(math.fma(-b, -math.inf, math.inf), math.inf)
self.assertEqual(math.fma(b, -math.inf, -math.inf), -math.inf)
with self.subTest(b=b):
self.assertEqual(math.fma(math.inf, b, math.inf), math.inf)
self.assertEqual(math.fma(math.inf, -b, -math.inf), -math.inf)
self.assertEqual(math.fma(-math.inf, -b, math.inf), math.inf)
self.assertEqual(math.fma(-math.inf, b, -math.inf), -math.inf)
self.assertEqual(math.fma(b, math.inf, math.inf), math.inf)
self.assertEqual(math.fma(-b, math.inf, -math.inf), -math.inf)
self.assertEqual(math.fma(-b, -math.inf, math.inf), math.inf)
self.assertEqual(math.fma(b, -math.inf, -math.inf), -math.inf)

# Infinite result when a*b finite, c infinite.
for a, b in itertools.product(finites, finites):
self.assertEqual(math.fma(a, b, math.inf), math.inf)
self.assertEqual(math.fma(a, b, -math.inf), -math.inf)
with self.subTest(b=b):
self.assertEqual(math.fma(a, b, math.inf), math.inf)
self.assertEqual(math.fma(a, b, -math.inf), -math.inf)

# Infinite result when a*b infinite, c finite.
for b, c in itertools.product(positives, finites):
self.assertEqual(math.fma(math.inf, b, c), math.inf)
self.assertEqual(math.fma(-math.inf, b, c), -math.inf)
self.assertEqual(math.fma(-math.inf, -b, c), math.inf)
self.assertEqual(math.fma(math.inf, -b, c), -math.inf)
with self.subTest(b=b, c=c):
self.assertEqual(math.fma(math.inf, b, c), math.inf)
self.assertEqual(math.fma(-math.inf, b, c), -math.inf)
self.assertEqual(math.fma(-math.inf, -b, c), math.inf)
self.assertEqual(math.fma(math.inf, -b, c), -math.inf)

self.assertEqual(math.fma(b, math.inf, c), math.inf)
self.assertEqual(math.fma(b, -math.inf, c), -math.inf)
self.assertEqual(math.fma(-b, -math.inf, c), math.inf)
self.assertEqual(math.fma(-b, math.inf, c), -math.inf)
self.assertEqual(math.fma(b, math.inf, c), math.inf)
self.assertEqual(math.fma(b, -math.inf, c), -math.inf)
self.assertEqual(math.fma(-b, -math.inf, c), math.inf)
self.assertEqual(math.fma(-b, math.inf, c), -math.inf)

# gh-73468: On some platforms, libc fma() doesn't implement IEE 754-2008
# properly: it doesn't use the right sign when the result is zero.
Expand All @@ -2770,23 +2776,24 @@ def test_fma_zero_result(self):

# Zero results from exact zero inputs.
for b in nonnegative_finites:
self.assertIsPositiveZero(math.fma(0.0, b, 0.0))
self.assertIsPositiveZero(math.fma(0.0, b, -0.0))
self.assertIsNegativeZero(math.fma(0.0, -b, -0.0))
self.assertIsPositiveZero(math.fma(0.0, -b, 0.0))
self.assertIsPositiveZero(math.fma(-0.0, -b, 0.0))
self.assertIsPositiveZero(math.fma(-0.0, -b, -0.0))
self.assertIsNegativeZero(math.fma(-0.0, b, -0.0))
self.assertIsPositiveZero(math.fma(-0.0, b, 0.0))

self.assertIsPositiveZero(math.fma(b, 0.0, 0.0))
self.assertIsPositiveZero(math.fma(b, 0.0, -0.0))
self.assertIsNegativeZero(math.fma(-b, 0.0, -0.0))
self.assertIsPositiveZero(math.fma(-b, 0.0, 0.0))
self.assertIsPositiveZero(math.fma(-b, -0.0, 0.0))
self.assertIsPositiveZero(math.fma(-b, -0.0, -0.0))
self.assertIsNegativeZero(math.fma(b, -0.0, -0.0))
self.assertIsPositiveZero(math.fma(b, -0.0, 0.0))
with self.subTest(b=b):
self.assertIsPositiveZero(math.fma(0.0, b, 0.0))
self.assertIsPositiveZero(math.fma(0.0, b, -0.0))
self.assertIsNegativeZero(math.fma(0.0, -b, -0.0))
self.assertIsPositiveZero(math.fma(0.0, -b, 0.0))
self.assertIsPositiveZero(math.fma(-0.0, -b, 0.0))
self.assertIsPositiveZero(math.fma(-0.0, -b, -0.0))
self.assertIsNegativeZero(math.fma(-0.0, b, -0.0))
self.assertIsPositiveZero(math.fma(-0.0, b, 0.0))

self.assertIsPositiveZero(math.fma(b, 0.0, 0.0))
self.assertIsPositiveZero(math.fma(b, 0.0, -0.0))
self.assertIsNegativeZero(math.fma(-b, 0.0, -0.0))
self.assertIsPositiveZero(math.fma(-b, 0.0, 0.0))
self.assertIsPositiveZero(math.fma(-b, -0.0, 0.0))
self.assertIsPositiveZero(math.fma(-b, -0.0, -0.0))
self.assertIsNegativeZero(math.fma(b, -0.0, -0.0))
self.assertIsPositiveZero(math.fma(b, -0.0, 0.0))

# Exact zero result from nonzero inputs.
self.assertIsPositiveZero(math.fma(2.0, 2.0, -4.0))
Expand Down Expand Up @@ -2892,12 +2899,14 @@ def test_random(self):
'0x1.f5467b1911fd6p-2', '0x1.b5cee3225caa5p-1'),
]
for a_hex, b_hex, c_hex, expected_hex in test_values:
a = float.fromhex(a_hex)
b = float.fromhex(b_hex)
c = float.fromhex(c_hex)
expected = float.fromhex(expected_hex)
self.assertEqual(math.fma(a, b, c), expected)
self.assertEqual(math.fma(b, a, c), expected)
with self.subTest(a_hex=a_hex, b_hex=b_hex, c_hex=c_hex,
expected_hex=expected_hex):
a = float.fromhex(a_hex)
b = float.fromhex(b_hex)
c = float.fromhex(c_hex)
expected = float.fromhex(expected_hex)
self.assertEqual(math.fma(a, b, c), expected)
self.assertEqual(math.fma(b, a, c), expected)

# Custom assertions.
def assertIsNaN(self, value):
Expand Down
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