From dadcd1fd50b02697efcc81cba0bd5b3b5083e69f Mon Sep 17 00:00:00 2001 From: Mark Dickinson Date: Fri, 1 Aug 2008 09:13:07 +0000 Subject: [PATCH] Tone down math.fsum warning. --- Doc/library/math.rst | 25 ++----------------------- 1 file changed, 2 insertions(+), 23 deletions(-) diff --git a/Doc/library/math.rst b/Doc/library/math.rst index 6f8d3c8aa0..be3b70bfcc 100644 --- a/Doc/library/math.rst +++ b/Doc/library/math.rst @@ -92,29 +92,8 @@ 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 -- 2.40.0