1 from test.test_support import TestFailed 2 3 # A test for SF bug 422177: manifest float constants varied way too much in 4 # precision depending on whether Python was loading a module for the first 5 # time, or reloading it from a precompiled .pyc. The "expected" failure 6 # mode is that when test_import imports this after all .pyc files have been 7 # erased, it passes, but when test_import imports this from 8 # double_const.pyc, it fails. This indicates a woeful loss of precision in 9 # the marshal format for doubles. It's also possible that repr() doesn't 10 # produce enough digits to get reasonable precision for this box. 11 12 PI = 3.14159265358979324 13 TWOPI = 6.28318530717958648 14 15 PI_str = "3.14159265358979324" 16 TWOPI_str = "6.28318530717958648" 17 18 # Verify that the double x is within a few bits of eval(x_str). 19 def check_ok(x, x_str): 20 assert x > 0.0 21 x2 = eval(x_str) 22 assert x2 > 0.0 23 diff = abs(x - x2) 24 # If diff is no larger than 3 ULP (wrt x2), then diff/8 is no larger 25 # than 0.375 ULP, so adding diff/8 to x2 should have no effect. 26 if x2 + (diff / 8.) != x2: 27 raise TestFailed("Manifest const %s lost too much precision " % x_str) 28 29 check_ok(PI, PI_str) 30 check_ok(TWOPI, TWOPI_str) 31
