Merge test_strtod and test_float string-to-float conversion tests.
This commit is contained in:
Mark Dickinson
parent
c733b3252f
commit
801923681c
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@ -8,7 +8,6 @@ import operator
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import random
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import fractions
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import sys
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import re
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INF = float("inf")
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NAN = float("nan")
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@ -22,74 +21,6 @@ requires_IEEE_754 = unittest.skipUnless(
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test_dir = os.path.dirname(__file__) or os.curdir
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format_testfile = os.path.join(test_dir, 'formatfloat_testcases.txt')
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finite_decimal_parser = re.compile(r""" # A numeric string consists of:
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(?P<sign>[-+])? # an optional sign, followed by
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(?=\d|\.\d) # a number with at least one digit
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(?P<int>\d*) # having a (possibly empty) integer part
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(?:\.(?P<frac>\d*))? # followed by an optional fractional part
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(?:E(?P<exp>[-+]?\d+))? # and an optional exponent
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\Z
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""", re.VERBOSE | re.IGNORECASE | re.UNICODE).match
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# Pure Python version of correctly rounded string->float conversion.
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# Avoids any use of floating-point by returning the result as a hex string.
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def strtod(s, mant_dig=53, min_exp = -1021, max_exp = 1024):
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"""Convert a finite decimal string to a hex string representing an
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IEEE 754 binary64 float. Return 'inf' or '-inf' on overflow.
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This function makes no use of floating-point arithmetic at any
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stage."""
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# parse string into a pair of integers 'a' and 'b' such that
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# abs(decimal value) = a/b, and a boolean 'negative'.
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m = finite_decimal_parser(s)
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if m is None:
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raise ValueError('invalid numeric string')
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fraction = m.group('frac') or ''
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intpart = int(m.group('int') + fraction)
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exp = int(m.group('exp') or '0') - len(fraction)
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negative = m.group('sign') == '-'
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a, b = intpart*10**max(exp, 0), 10**max(0, -exp)
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# quick return for zeros
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if not a:
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return '-0x0.0p+0' if negative else '0x0.0p+0'
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# compute exponent e for result; may be one too small in the case
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# that the rounded value of a/b lies in a different binade from a/b
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d = a.bit_length() - b.bit_length()
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d += (a >> d if d >= 0 else a << -d) >= b
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e = max(d, min_exp) - mant_dig
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# approximate a/b by number of the form q * 2**e; adjust e if necessary
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a, b = a << max(-e, 0), b << max(e, 0)
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q, r = divmod(a, b)
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if 2*r > b or 2*r == b and q & 1:
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q += 1
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if q.bit_length() == mant_dig+1:
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q //= 2
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e += 1
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# double check that (q, e) has the right form
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assert q.bit_length() <= mant_dig and e >= min_exp - mant_dig
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assert q.bit_length() == mant_dig or e == min_exp - mant_dig
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# check for overflow and underflow
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if e + q.bit_length() > max_exp:
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return '-inf' if negative else 'inf'
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if not q:
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return '-0x0.0p+0' if negative else '0x0.0p+0'
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# for hex representation, shift so # bits after point is a multiple of 4
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hexdigs = 1 + (mant_dig-2)//4
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shift = 3 - (mant_dig-2)%4
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q, e = q << shift, e - shift
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return '{}0x{:x}.{:0{}x}p{:+d}'.format(
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'-' if negative else '',
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q // 16**hexdigs,
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q % 16**hexdigs,
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hexdigs,
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e + 4*hexdigs)
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class GeneralFloatCases(unittest.TestCase):
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def test_float(self):
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@ -1378,38 +1309,6 @@ class HexFloatTestCase(unittest.TestCase):
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else:
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self.identical(x, fromHex(toHex(x)))
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class StrtodTestCase(unittest.TestCase):
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def check_string(self, s):
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expected = strtod(s)
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try:
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fs = float(s)
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except OverflowError:
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got = '-inf' if s[0] == '-' else 'inf'
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else:
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got = fs.hex()
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self.assertEqual(expected, got,
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"Incorrectly rounded str->float conversion for "
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"{}: expected {}, got {}".format(s, expected, got))
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@unittest.skipUnless(getattr(sys, 'float_repr_style', '') == 'short',
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"applies only when using short float repr style")
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def test_bug7632(self):
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# check a few particular values that gave incorrectly rounded
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# results with previous versions of dtoa.c
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test_strings = [
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'94393431193180696942841837085033647913224148539854e-358',
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'12579816049008305546974391768996369464963024663104e-357',
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'17489628565202117263145367596028389348922981857013e-357',
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'18487398785991994634182916638542680759613590482273e-357',
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'32002864200581033134358724675198044527469366773928e-358',
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'73608278998966969345824653500136787876436005957953e-358',
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'64774478836417299491718435234611299336288082136054e-358',
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'13704940134126574534878641876947980878824688451169e-357',
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'46697445774047060960624497964425416610480524760471e-358',
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]
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for s in test_strings:
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self.check_string(s)
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def test_main():
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test_support.run_unittest(
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@ -1421,7 +1320,6 @@ def test_main():
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RoundTestCase,
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InfNanTest,
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HexFloatTestCase,
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StrtodTestCase,
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)
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if __name__ == '__main__':
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@ -23,6 +23,8 @@ strtod_parser = re.compile(r""" # A numeric string consists of:
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\Z
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""", re.VERBOSE | re.IGNORECASE).match
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# Pure Python version of correctly rounded string->float conversion.
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# Avoids any use of floating-point by returning the result as a hex string.
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def strtod(s, mant_dig=53, min_exp = -1021, max_exp = 1024):
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"""Convert a finite decimal string to a hex string representing an
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IEEE 754 binary64 float. Return 'inf' or '-inf' on overflow.
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@ -259,6 +261,10 @@ class StrtodTests(unittest.TestCase):
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'18487398785991994634182916638542680759613590482273e-357',
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'32002864200581033134358724675198044527469366773928e-358',
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'94393431193180696942841837085033647913224148539854e-358',
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'73608278998966969345824653500136787876436005957953e-358',
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'64774478836417299491718435234611299336288082136054e-358',
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'13704940134126574534878641876947980878824688451169e-357',
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'46697445774047060960624497964425416610480524760471e-358',
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# failing case for bug introduced by METD in r77451 (attempted
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# fix for issue 7632, bug 2), and fixed in r77482.
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'28639097178261763178489759107321392745108491825303e-311',
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