GH-100425: Note improved commutativity in sum().

Doc/library/functions.rst

@@ -56,7 +56,7 @@
 
 .. function:: abs(x)
 
    Return the absolute value of a number.  The argument may be an
    integer, a floating point number, or an object implementing :meth:`__abs__`.
    If the argument is a complex number, its magnitude is returned.
 
@@ -231,7 +231,7 @@
 
 .. function:: callable(object)
 
    Return :const:`True` if the *object* argument appears callable,
    :const:`False` if not.  If this returns ``True``, it is still possible that a
    call fails, but if it is ``False``, calling *object* will never succeed.
    Note that classes are callable (calling a class returns a new instance);
@@ -318,7 +318,7 @@
    non-zero integer then the *flags* argument is it -- the flags (future
    features and compiler options) in the surrounding code are ignored.
 
    Compiler options and future statements are specified by bits which can be
    bitwise ORed together to specify multiple options. The bitfield required to
    specify a given future feature can be found as the
    :attr:`~__future__._Feature.compiler_flag` attribute on the
@@ -432,12 +432,12 @@
    Without arguments, return the list of names in the current local scope.  With an
    argument, attempt to return a list of valid attributes for that object.
 
    If the object has a method named :meth:`__dir__`, this method will be called and
    must return the list of attributes. This allows objects that implement a custom
    :func:`__getattr__` or :func:`__getattribute__` function to customize the way
    :func:`dir` reports their attributes.
 
    If the object does not provide :meth:`__dir__`, the function tries its best to
    gather information from the object's :attr:`~object.__dict__` attribute, if defined, and
    from its type object.  The resulting list is not necessarily complete and may
    be inaccurate when the object has a custom :func:`__getattr__`.
@@ -660,7 +660,7 @@
    input must conform to the ``floatvalue`` production rule in the following
    grammar, after leading and trailing whitespace characters are removed:
 
    .. productionlist:: float
       sign: "+" | "-"
       infinity: "Infinity" | "inf"
       nan: "nan"
@@ -1752,7 +1752,7 @@
       The *start* parameter can be specified as a keyword argument.
 
    .. versionchanged:: 3.12 Summation of floats switched to an algorithm
-      that gives higher accuracy on most builds.
+      that gives higher accuracy and better commutativity on most builds.
 
 
 .. class:: super()

Doc/whatsnew/3.12.rst

@@ -504,8 +504,8 @@ Other Language Changes
 * :class:`slice` objects are now hashable, allowing them to be used as dict keys and
   set items. (Contributed by Will Bradshaw, Furkan Onder, and Raymond Hettinger in :gh:`101264`.)
 
-* :func:`sum` now uses Neumaier summation to improve accuracy when summing
-  floats or mixed ints and floats.
+* :func:`sum` now uses Neumaier summation to improve accuracy and commutativity
+  when summing floats or mixed ints and floats.
   (Contributed by Raymond Hettinger in :gh:`100425`.)
 
 * Exceptions raised in a typeobject's ``__set_name__`` method are no longer