0001 from test.test_support import TestFailed 0002 0003 # A test for SF bug 422177: manifest float constants varied way too much in 0004 # precision depending on whether Python was loading a module for the first 0005 # time, or reloading it from a precompiled .pyc. The "expected" failure 0006 # mode is that when test_import imports this after all .pyc files have been 0007 # erased, it passes, but when test_import imports this from 0008 # double_const.pyc, it fails. This indicates a woeful loss of precision in 0009 # the marshal format for doubles. It's also possible that repr() doesn't 0010 # produce enough digits to get reasonable precision for this box. 0011 0012 PI = 3.14159265358979324 0013 TWOPI = 6.28318530717958648 0014 0015 PI_str = "3.14159265358979324" 0016 TWOPI_str = "6.28318530717958648" 0017 0018 # Verify that the double x is within a few bits of eval(x_str). 0019 def check_ok(x, x_str): 0020 assert x > 0.0 0021 x2 = eval(x_str) 0022 assert x2 > 0.0 0023 diff = abs(x - x2) 0024 # If diff is no larger than 3 ULP (wrt x2), then diff/8 is no larger 0025 # than 0.375 ULP, so adding diff/8 to x2 should have no effect. 0026 if x2 + (diff / 8.) != x2: 0027 raise TestFailed("Manifest const %s lost too much precision " % x_str) 0028 0029 check_ok(PI, PI_str) 0030 check_ok(TWOPI, TWOPI_str) 0031
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