mirror of
https://github.com/wassname/segpy.git
synced 2026-06-27 20:06:49 +08:00
Robert Smallshire
269 lines
9.4 KiB
Python
269 lines
9.4 KiB
Python
from math import trunc, floor
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import unittest
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from hypothesis import given, assume
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from hypothesis.descriptors import integers_in_range, floats_in_range
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from segpy.portability import byte_string
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from segpy.ibm_float import (ieee2ibm, ibm2ieee, MAX_IBM_FLOAT, SMALLEST_POSITIVE_NORMAL_IBM_FLOAT,
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LARGEST_NEGATIVE_NORMAL_IBM_FLOAT, MIN_IBM_FLOAT, IBMFloat, EPSILON_IBM_FLOAT, truncate,
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MAX_EXACT_INTEGER_IBM_FLOAT, MIN_EXACT_INTEGER_IBM_FLOAT, EXPONENT_BIAS)
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from segpy.util import almost_equal
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class Ibm2Ieee(unittest.TestCase):
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def test_zero(self):
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self.assertEqual(ibm2ieee(b'\0\0\0\0'), 0.0)
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def test_positive_half(self):
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self.assertEqual(ibm2ieee(byte_string((0b11000000, 0x80, 0x00, 0x00))), -0.5)
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def test_negative_half(self):
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self.assertEqual(ibm2ieee(byte_string((0b01000000, 0x80, 0x00, 0x00))), 0.5)
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def test_one(self):
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self.assertEqual(ibm2ieee(b'\x41\x10\x00\x00'), 1.0)
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def test_negative_118_625(self):
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# Example taken from Wikipedia http://en.wikipedia.org/wiki/IBM_Floating_Point_Architecture
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self.assertEqual(ibm2ieee(byte_string((0b11000010, 0b01110110, 0b10100000, 0b00000000))), -118.625)
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def test_largest_representable_number(self):
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self.assertEqual(ibm2ieee(byte_string((0b01111111, 0b11111111, 0b11111111, 0b11111111))), MAX_IBM_FLOAT)
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def test_smallest_positive_normalised_number(self):
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self.assertEqual(ibm2ieee(byte_string((0b00000000, 0b00010000, 0b00000000, 0b00000000))), SMALLEST_POSITIVE_NORMAL_IBM_FLOAT)
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def test_largest_negative_normalised_number(self):
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self.assertEqual(ibm2ieee(byte_string((0b10000000, 0b00010000, 0b00000000, 0b00000000))), LARGEST_NEGATIVE_NORMAL_IBM_FLOAT)
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def test_smallest_representable_number(self):
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self.assertEqual(ibm2ieee(byte_string((0b11111111, 0b11111111, 0b11111111, 0b11111111))), MIN_IBM_FLOAT)
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def test_error_1(self):
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self.assertEqual(ibm2ieee(byte_string((196, 74, 194, 143))), -19138.55859375)
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def test_error_2(self):
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self.assertEqual(ibm2ieee(byte_string((191, 128, 0, 0))), -0.03125)
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def test_subnormal(self):
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self.assertEqual(ibm2ieee(byte_string((0x00, 0x00, 0x00, 0x20))), 1.6472184286297693e-83)
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def test_subnormal_is_subnormal(self):
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self.assertTrue(0 < ibm2ieee(byte_string((0x00, 0x00, 0x00, 0x20))) < SMALLEST_POSITIVE_NORMAL_IBM_FLOAT)
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def test_subnormal_smallest_subnormal(self):
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self.assertEqual(ibm2ieee(byte_string((0x00, 0x00, 0x00, 0x01))), 5.147557589468029e-85)
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class Ieee2Ibm(unittest.TestCase):
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def test_zero(self):
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self.assertEqual(ieee2ibm(0.0), b'\0\0\0\0')
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def test_positive_half(self):
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self.assertEqual(ieee2ibm(-0.5), byte_string((0b11000000, 0x80, 0x00, 0x00)))
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def test_negative_half(self):
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self.assertEqual(ieee2ibm(0.5), byte_string((0b01000000, 0x80, 0x00, 0x00)))
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def test_one(self):
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self.assertEqual(ieee2ibm(1.0), b'\x41\x10\x00\x00')
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def test_negative_118_625(self):
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# Example taken from Wikipedia http://en.wikipedia.org/wiki/IBM_Floating_Point_Architecture
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self.assertEqual(ieee2ibm(-118.625), byte_string((0b11000010, 0b01110110, 0b10100000, 0b00000000)))
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def test_0_1(self):
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# Note, this is different from the Wikipedia example, because the Wikipedia example does
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# round to nearest, and our routine does round to zero
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self.assertEqual(ieee2ibm(0.1), byte_string((0b01000000, 0b00011001, 0b10011001, 0b10011001)))
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def test_subnormal(self):
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self.assertEqual(ieee2ibm(1.6472184286297693e-83), byte_string((0x00, 0x00, 0x00, 0x20)))
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def test_smallest_subnormal(self):
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self.assertEqual(ieee2ibm(5.147557589468029e-85), byte_string((0x00, 0x00, 0x00, 0x01)))
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def test_too_small_subnormal(self):
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with self.assertRaises(FloatingPointError):
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ieee2ibm(1e-86)
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def test_nan(self):
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with self.assertRaises(ValueError):
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ieee2ibm(float('nan'))
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def test_inf(self):
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with self.assertRaises(ValueError):
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ieee2ibm(float('inf'))
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def test_too_large(self):
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with self.assertRaises(OverflowError):
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ieee2ibm(MAX_IBM_FLOAT * 10)
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def test_too_small(self):
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with self.assertRaises(OverflowError):
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ieee2ibm(MIN_IBM_FLOAT * 10)
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class Ibm2IeeeRoundtrip(unittest.TestCase):
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def test_zero(self):
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ibm_start = b'\0\0\0\0'
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f = ibm2ieee(ibm_start)
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ibm_result = ieee2ibm(f)
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self.assertEqual(ibm_start, ibm_result)
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def test_positive_half(self):
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ibm_start = byte_string((0b11000000, 0x80, 0x00, 0x00))
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f = ibm2ieee(ibm_start)
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ibm_result = ieee2ibm(f)
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self.assertEqual(ibm_start, ibm_result)
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def test_negative_half(self):
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ibm_start = byte_string((0b01000000, 0x80, 0x00, 0x00))
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f = ibm2ieee(ibm_start)
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ibm_result = ieee2ibm(f)
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self.assertEqual(ibm_start, ibm_result)
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def test_one(self):
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ibm_start = b'\x41\x10\x00\x00'
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f = ibm2ieee(ibm_start)
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ibm_result = ieee2ibm(f)
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self.assertEqual(ibm_start, ibm_result)
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def test_subnormal(self):
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ibm_start = byte_string((0x00, 0x00, 0x00, 0x20))
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f = ibm2ieee(ibm_start)
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ibm_result = ieee2ibm(f)
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self.assertEqual(ibm_start, ibm_result)
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class TestIBMFloat(unittest.TestCase):
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def test_zero_from_float(self):
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zero = IBMFloat.from_float(0.0)
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self.assertTrue(zero.is_zero())
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def test_zero_from_bytes(self):
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zero = IBMFloat.from_bytes(b'\x00\x00\x00\x00')
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self.assertTrue(zero.is_zero())
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def test_subnormal(self):
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ibm = IBMFloat.from_float(1.6472184286297693e-83)
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self.assertTrue(ibm.is_subnormal())
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def test_smallest_subnormal(self):
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ibm = IBMFloat.from_float(5.147557589468029e-85)
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self.assertEqual(bytes(ibm), byte_string((0x00, 0x00, 0x00, 0x01)))
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def test_too_small_subnormal(self):
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with self.assertRaises(FloatingPointError):
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IBMFloat.from_float(1e-86)
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def test_nan(self):
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with self.assertRaises(ValueError):
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IBMFloat.from_float(float('nan'))
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def test_inf(self):
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with self.assertRaises(ValueError):
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IBMFloat.from_float(float('inf'))
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def test_too_large(self):
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with self.assertRaises(OverflowError):
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IBMFloat.from_float(MAX_IBM_FLOAT * 10)
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def test_too_small(self):
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with self.assertRaises(OverflowError):
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IBMFloat.from_float(MIN_IBM_FLOAT * 10)
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@given(float)
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def test_bool(self, f):
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self.assertEqual(bool(IBMFloat.from_float(f)), bool(f))
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@given(integers_in_range(0, 255),
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integers_in_range(0, 255),
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integers_in_range(0, 255),
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integers_in_range(0, 255))
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def test_bytes_roundtrip(self, a, b, c, d):
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b = byte_string((a, b, c, d))
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ibm = IBMFloat.from_bytes(b)
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self.assertEqual(bytes(ibm), b)
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@given(floats_in_range(MIN_IBM_FLOAT, MAX_IBM_FLOAT))
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def test_floats_roundtrip(self, f):
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ibm = IBMFloat.from_float(f)
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self.assertTrue(almost_equal(f, float(ibm), epsilon=EPSILON_IBM_FLOAT))
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@given(integers_in_range(0, MAX_EXACT_INTEGER_IBM_FLOAT - 1))
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@given(floats_in_range(0.0, 1.0))
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def test_trunc_above_zero(self, i, f):
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assume(f != 1.0)
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ieee = i + f
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ibm = IBMFloat.from_float(ieee)
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self.assertEqual(trunc(ibm), i)
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@given(integers_in_range(MIN_EXACT_INTEGER_IBM_FLOAT + 1, 0))
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@given(floats_in_range(0.0, 1.0))
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def test_trunc_below_zero(self, i, f):
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assume(f != 1.0)
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ieee = i - f
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ibm = IBMFloat.from_float(ieee)
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self.assertEqual(trunc(ibm), i)
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def test_normalise_subnormal_expect_failure(self):
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# This float has an base-16 exponent of -64 (the minimum) and cannot be normalised
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ibm = IBMFloat.from_float(1.6472184286297693e-83)
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assert ibm.is_subnormal()
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with self.assertRaises(FloatingPointError):
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ibm.normalize()
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def test_normalise_subnormal(self):
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ibm = IBMFloat.from_bytes((0b01000000, 0b00000000, 0b11111111, 0b00000000))
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assert ibm.is_subnormal()
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normalized = ibm.normalize()
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self.assertFalse(normalized.is_subnormal())
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def test_normalise_subnormal2(self):
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ibm = IBMFloat.from_bytes((64, 1, 0, 0))
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assert ibm.is_subnormal()
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normalized = ibm.normalize()
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self.assertFalse(normalized.is_subnormal())
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@given(integers_in_range(128, 255),
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integers_in_range(0, 255),
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integers_in_range(0, 255),
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integers_in_range(4, 23))
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def test_normalise_subnormal(self, b, c, d, shift):
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mantissa = (b << 16) | (c << 8) | d
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assume(mantissa != 0)
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mantissa >>= shift
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assert mantissa != 0
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sa = EXPONENT_BIAS
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sb = (mantissa >> 16) & 0xff
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sc = (mantissa >> 8) & 0xff
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sd = mantissa & 0xff
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ibm = IBMFloat.from_bytes((sa, sb, sc, sd))
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assert ibm.is_subnormal()
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normalized = ibm.normalize()
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self.assertFalse(normalized.is_subnormal())
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@given(integers_in_range(0, 255),
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integers_in_range(0, 255),
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integers_in_range(0, 255),
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integers_in_range(0, 255))
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def test_abs(self, a, b, c, d):
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b = byte_string((a, b, c, d))
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ibm = IBMFloat.from_bytes(b)
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abs_ibm = abs(ibm)
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self.assertGreaterEqual(abs_ibm.signbit, 0)
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if __name__ == '__main__':
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unittest.main()
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