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- from test.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)
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