Commit | Line | Data |
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920dae64 AT |
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) |