31 lines
1.2 KiB
Python
31 lines
1.2 KiB
Python
from test.support import TestFailed
|
|
|
|
# A test for SF bug 422177: manifest float constants varied way too much in
|
|
# precision depending on whether Python was loading a module for the first
|
|
# time, or reloading it from a precompiled .pyc. The "expected" failure
|
|
# mode is that when test_import imports this after all .pyc files have been
|
|
# erased, it passes, but when test_import imports this from
|
|
# double_const.pyc, it fails. This indicates a woeful loss of precision in
|
|
# the marshal format for doubles. It's also possible that repr() doesn't
|
|
# produce enough digits to get reasonable precision for this box.
|
|
|
|
PI = 3.14159265358979324
|
|
TWOPI = 6.28318530717958648
|
|
|
|
PI_str = "3.14159265358979324"
|
|
TWOPI_str = "6.28318530717958648"
|
|
|
|
# Verify that the double x is within a few bits of eval(x_str).
|
|
def check_ok(x, x_str):
|
|
assert x > 0.0
|
|
x2 = eval(x_str)
|
|
assert x2 > 0.0
|
|
diff = abs(x - x2)
|
|
# If diff is no larger than 3 ULP (wrt x2), then diff/8 is no larger
|
|
# than 0.375 ULP, so adding diff/8 to x2 should have no effect.
|
|
if x2 + (diff / 8.) != x2:
|
|
raise TestFailed("Manifest const %s lost too much precision " % x_str)
|
|
|
|
check_ok(PI, PI_str)
|
|
check_ok(TWOPI, TWOPI_str)
|