| 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) |
