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Diffstat (limited to 'Doc/library/math.rst')
| -rw-r--r-- | Doc/library/math.rst | 25 |
1 files changed, 2 insertions, 23 deletions
diff --git a/Doc/library/math.rst b/Doc/library/math.rst index df4ec1b..da38305 100644 --- a/Doc/library/math.rst +++ b/Doc/library/math.rst @@ -85,29 +85,8 @@ Number-theoretic and representation functions: .. note:: - On platforms where arithmetic results are not correctly rounded, - :func:`fsum` may occasionally produce incorrect results; these - results should be no less accurate than those from the builtin - :func:`sum` function, but nevertheless may have arbitrarily - large relative error. - - In particular, this affects some older Intel hardware (for - example Pentium and earlier x86 processors) that makes use of - 'extended precision' floating-point registers with 64 bits of - precision instead of the 53 bits of precision provided by a C - double. Arithmetic operations using these registers may be - doubly rounded (rounded first to 64 bits, and then rerounded to - 53 bits), leading to incorrectly rounded results. To test - whether your machine is one of those affected, try the following - at a Python prompt:: - - >>> 1e16 + 2.9999 - 10000000000000002.0 - - Machines subject to the double-rounding problem described above - are likely to print ``10000000000000004.0`` instead of - ``10000000000000002.0``. - + The accuracy of fsum() may be impaired on builds that use + extended precision addition and then double-round the results. .. versionadded:: 2.6 |