LWG2932 Constraints on parallel algorithm implementations are underspecified

[algorithms.parallel.exec]/p1 Fixed punctuation.

Author: Dawn Perchik

source/algorithms.tex

@@ -1294,6 +1294,19 @@
 which describe the manner in which the execution of these algorithms may be
 parallelized and the manner in which they apply the element access functions.
 
+\pnum
+If an object is modified by an element access function,
+the algorithm will perform no other unsynchronized accesses to that object.
+The modifying element access functions are those
+which are specified as modifying the object in the relevant concept.
+\begin{note}
+For example,
+\tcode{swap()}, \tcode{++}, \tcode{--}, \tcode{@=}, and assignments
+modify the object.
+For the assignment and \tcode{@=} operators,
+only the left argument is modified.
+\end{note}
+
 \pnum
 Unless otherwise stated, implementations may make arbitrary copies of elements
 (with type \tcode{T}) from sequences where \tcode{is_trivially_copy_constructible_v<T>}