Merge test_strtod and test_float string-to-float conversion tests.

This commit is contained in:
Mark Dickinson 2010-06-20 18:50:19 +00:00
parent c733b3252f
commit 801923681c
2 changed files with 6 additions and 102 deletions

View File

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

View File

@ -23,6 +23,8 @@ strtod_parser = re.compile(r""" # A numeric string consists of:
\Z
""", re.VERBOSE | re.IGNORECASE).match
# Pure Python version of correctly rounded string->float conversion.
# Avoids any use of floating-point by returning the result as a hex string.
def strtod(s, mant_dig=53, min_exp = -1021, max_exp = 1024):
"""Convert a finite decimal string to a hex string representing an
IEEE 754 binary64 float. Return 'inf' or '-inf' on overflow.
@ -259,6 +261,10 @@ class StrtodTests(unittest.TestCase):
'18487398785991994634182916638542680759613590482273e-357',
'32002864200581033134358724675198044527469366773928e-358',
'94393431193180696942841837085033647913224148539854e-358',
'73608278998966969345824653500136787876436005957953e-358',
'64774478836417299491718435234611299336288082136054e-358',
'13704940134126574534878641876947980878824688451169e-357',
'46697445774047060960624497964425416610480524760471e-358',
# failing case for bug introduced by METD in r77451 (attempted
# fix for issue 7632, bug 2), and fixed in r77482.
'28639097178261763178489759107321392745108491825303e-311',