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Unified Diff: Modules/_decimal/tests/randfloat.py

Issue 7652: Merge C version of decimal into py3k.
Patch Set: Created 7 years, 8 months ago
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/Modules/_decimal/tests/randfloat.py Sat Mar 10 18:12:20 2012 +0100
@@ -0,0 +1,250 @@
+# Copyright (c) 2010 Python Software Foundation. All Rights Reserved.
+# Adapted from Python's Lib/test/test_strtod.py (by Mark Dickinson)
+
+# More test cases for deccheck.py.
+
+import random
+
+TEST_SIZE = 2
+
+
+def test_short_halfway_cases():
+ # exact halfway cases with a small number of significant digits
+ for k in 0, 5, 10, 15, 20:
+ # upper = smallest integer >= 2**54/5**k
+ upper = -(-2**54//5**k)
+ # lower = smallest odd number >= 2**53/5**k
+ lower = -(-2**53//5**k)
+ if lower % 2 == 0:
+ lower += 1
+ for i in range(10 * TEST_SIZE):
+ # Select a random odd n in [2**53/5**k,
+ # 2**54/5**k). Then n * 10**k gives a halfway case
+ # with small number of significant digits.
+ n, e = random.randrange(lower, upper, 2), k
+
+ # Remove any additional powers of 5.
+ while n % 5 == 0:
+ n, e = n // 5, e + 1
+ assert n % 10 in (1, 3, 7, 9)
+
+ # Try numbers of the form n * 2**p2 * 10**e, p2 >= 0,
+ # until n * 2**p2 has more than 20 significant digits.
+ digits, exponent = n, e
+ while digits < 10**20:
+ s = '{}e{}'.format(digits, exponent)
+ yield s
+ # Same again, but with extra trailing zeros.
+ s = '{}e{}'.format(digits * 10**40, exponent - 40)
+ yield s
+ digits *= 2
+
+ # Try numbers of the form n * 5**p2 * 10**(e - p5), p5
+ # >= 0, with n * 5**p5 < 10**20.
+ digits, exponent = n, e
+ while digits < 10**20:
+ s = '{}e{}'.format(digits, exponent)
+ yield s
+ # Same again, but with extra trailing zeros.
+ s = '{}e{}'.format(digits * 10**40, exponent - 40)
+ yield s
+ digits *= 5
+ exponent -= 1
+
+def test_halfway_cases():
+ # test halfway cases for the round-half-to-even rule
+ for i in range(1000):
+ for j in range(TEST_SIZE):
+ # bit pattern for a random finite positive (or +0.0) float
+ bits = random.randrange(2047*2**52)
+
+ # convert bit pattern to a number of the form m * 2**e
+ e, m = divmod(bits, 2**52)
+ if e:
+ m, e = m + 2**52, e - 1
+ e -= 1074
+
+ # add 0.5 ulps
+ m, e = 2*m + 1, e - 1
+
+ # convert to a decimal string
+ if e >= 0:
+ digits = m << e
+ exponent = 0
+ else:
+ # m * 2**e = (m * 5**-e) * 10**e
+ digits = m * 5**-e
+ exponent = e
+ s = '{}e{}'.format(digits, exponent)
+ yield s
+
+def test_boundaries():
+ # boundaries expressed as triples (n, e, u), where
+ # n*10**e is an approximation to the boundary value and
+ # u*10**e is 1ulp
+ boundaries = [
+ (10000000000000000000, -19, 1110), # a power of 2 boundary (1.0)
+ (17976931348623159077, 289, 1995), # overflow boundary (2.**1024)
+ (22250738585072013831, -327, 4941), # normal/subnormal (2.**-1022)
+ (0, -327, 4941), # zero
+ ]
+ for n, e, u in boundaries:
+ for j in range(1000):
+ for i in range(TEST_SIZE):
+ digits = n + random.randrange(-3*u, 3*u)
+ exponent = e
+ s = '{}e{}'.format(digits, exponent)
+ yield s
+ n *= 10
+ u *= 10
+ e -= 1
+
+def test_underflow_boundary():
+ # test values close to 2**-1075, the underflow boundary; similar
+ # to boundary_tests, except that the random error doesn't scale
+ # with n
+ for exponent in range(-400, -320):
+ base = 10**-exponent // 2**1075
+ for j in range(TEST_SIZE):
+ digits = base + random.randrange(-1000, 1000)
+ s = '{}e{}'.format(digits, exponent)
+ yield s
+
+def test_bigcomp():
+ for ndigs in 5, 10, 14, 15, 16, 17, 18, 19, 20, 40, 41, 50:
+ dig10 = 10**ndigs
+ for i in range(100 * TEST_SIZE):
+ digits = random.randrange(dig10)
+ exponent = random.randrange(-400, 400)
+ s = '{}e{}'.format(digits, exponent)
+ yield s
+
+def test_parsing():
+ # make '0' more likely to be chosen than other digits
+ digits = '000000123456789'
+ signs = ('+', '-', '')
+
+ # put together random short valid strings
+ # \d*[.\d*]?e
+ for i in range(1000):
+ for j in range(TEST_SIZE):
+ s = random.choice(signs)
+ intpart_len = random.randrange(5)
+ s += ''.join(random.choice(digits) for _ in range(intpart_len))
+ if random.choice([True, False]):
+ s += '.'
+ fracpart_len = random.randrange(5)
+ s += ''.join(random.choice(digits)
+ for _ in range(fracpart_len))
+ else:
+ fracpart_len = 0
+ if random.choice([True, False]):
+ s += random.choice(['e', 'E'])
+ s += random.choice(signs)
+ exponent_len = random.randrange(1, 4)
+ s += ''.join(random.choice(digits)
+ for _ in range(exponent_len))
+
+ if intpart_len + fracpart_len:
+ yield s
+
+test_particular = [
+ # squares
+ '1.00000000100000000025',
+ '1.0000000000000000000000000100000000000000000000000' #...
+ '00025',
+ '1.0000000000000000000000000000000000000000000010000' #...
+ '0000000000000000000000000000000000000000025',
+ '1.0000000000000000000000000000000000000000000000000' #...
+ '000001000000000000000000000000000000000000000000000' #...
+ '000000000025',
+ '0.99999999900000000025',
+ '0.9999999999999999999999999999999999999999999999999' #...
+ '999000000000000000000000000000000000000000000000000' #...
+ '000025',
+ '0.9999999999999999999999999999999999999999999999999' #...
+ '999999999999999999999999999999999999999999999999999' #...
+ '999999999999999999999999999999999999999990000000000' #...
+ '000000000000000000000000000000000000000000000000000' #...
+ '000000000000000000000000000000000000000000000000000' #...
+ '0000000000000000000000000000025',
+
+ '1.0000000000000000000000000000000000000000000000000' #...
+ '000000000000000000000000000000000000000000000000000' #...
+ '100000000000000000000000000000000000000000000000000' #...
+ '000000000000000000000000000000000000000000000000001',
+ '1.0000000000000000000000000000000000000000000000000' #...
+ '000000000000000000000000000000000000000000000000000' #...
+ '500000000000000000000000000000000000000000000000000' #...
+ '000000000000000000000000000000000000000000000000005',
+ '1.0000000000000000000000000000000000000000000000000' #...
+ '000000000100000000000000000000000000000000000000000' #...
+ '000000000000000000250000000000000002000000000000000' #...
+ '000000000000000000000000000000000000000000010000000' #...
+ '000000000000000000000000000000000000000000000000000' #...
+ '0000000000000000001',
+ '1.0000000000000000000000000000000000000000000000000' #...
+ '000000000100000000000000000000000000000000000000000' #...
+ '000000000000000000249999999999999999999999999999999' #...
+ '999999999999979999999999999999999999999999999999999' #...
+ '999999999999999999999900000000000000000000000000000' #...
+ '000000000000000000000000000000000000000000000000000' #...
+ '00000000000000000000000001',
+
+ '0.9999999999999999999999999999999999999999999999999' #...
+ '999999999900000000000000000000000000000000000000000' #...
+ '000000000000000000249999999999999998000000000000000' #...
+ '000000000000000000000000000000000000000000010000000' #...
+ '000000000000000000000000000000000000000000000000000' #...
+ '0000000000000000001',
+ '0.9999999999999999999999999999999999999999999999999' #...
+ '999999999900000000000000000000000000000000000000000' #...
+ '000000000000000000250000001999999999999999999999999' #...
+ '999999999999999999999999999999999990000000000000000' #...
+ '000000000000000000000000000000000000000000000000000' #...
+ '1',
+
+ # tough cases for ln etc.
+ '1.000000000000000000000000000000000000000000000000' #...
+ '00000000000000000000000000000000000000000000000000' #...
+ '00100000000000000000000000000000000000000000000000' #...
+ '00000000000000000000000000000000000000000000000000' #...
+ '0001',
+ '0.999999999999999999999999999999999999999999999999' #...
+ '99999999999999999999999999999999999999999999999999' #...
+ '99899999999999999999999999999999999999999999999999' #...
+ '99999999999999999999999999999999999999999999999999' #...
+ '99999999999999999999999999999999999999999999999999' #...
+ '9999'
+ ]
+
+
+TESTCASES = [
+ [x for x in test_short_halfway_cases()],
+ [x for x in test_halfway_cases()],
+ [x for x in test_boundaries()],
+ [x for x in test_underflow_boundary()],
+ [x for x in test_bigcomp()],
+ [x for x in test_parsing()],
+ test_particular
+]
+
+def un_randfloat():
+ for i in range(1000):
+ l = random.choice(TESTCASES[:6])
+ yield random.choice(l)
+ for v in test_particular:
+ yield v
+
+def bin_randfloat():
+ for i in range(1000):
+ l1 = random.choice(TESTCASES)
+ l2 = random.choice(TESTCASES)
+ yield random.choice(l1), random.choice(l2)
+
+def tern_randfloat():
+ for i in range(1000):
+ l1 = random.choice(TESTCASES)
+ l2 = random.choice(TESTCASES)
+ l3 = random.choice(TESTCASES)
+ yield random.choice(l1), random.choice(l2), random.choice(l3)
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