GH-100485: Add math.sumprod() (GH-100677)

2 files changed, 18 insertions, 9 deletions

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 4ad679d..e7d2e13 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -33,7 +33,7 @@ by combining :func:`map` and :func:`count` to form ``map(f, count())``.
 These tools and their built-in counterparts also work well with the high-speed
 functions in the :mod:`operator` module.  For example, the multiplication
 operator can be mapped across two vectors to form an efficient dot-product:
-``sum(map(operator.mul, vector1, vector2))``.
+``sum(starmap(operator.mul, zip(vec1, vec2, strict=True)))``.
 
 
 **Infinite iterators:**
@@ -838,10 +838,6 @@ which incur interpreter overhead.
        "Returns the sequence elements n times"
        return chain.from_iterable(repeat(tuple(iterable), n))
 
-   def dotproduct(vec1, vec2):
-       "Compute a sum of products."
-       return sum(starmap(operator.mul, zip(vec1, vec2, strict=True)))
-
    def convolve(signal, kernel):
        # See:  https://betterexplained.com/articles/intuitive-convolution/
        # convolve(data, [0.25, 0.25, 0.25, 0.25]) --> Moving average (blur)
@@ -852,7 +848,7 @@ which incur interpreter overhead.
        window = collections.deque([0], maxlen=n) * n
        for x in chain(signal, repeat(0, n-1)):
            window.append(x)
-           yield dotproduct(kernel, window)
+           yield math.sumprod(kernel, window)
 
    def polynomial_from_roots(roots):
        """Compute a polynomial's coefficients from its roots.
@@ -1211,9 +1207,6 @@ which incur interpreter overhead.
     >>> list(ncycles('abc', 3))
     ['a', 'b', 'c', 'a', 'b', 'c', 'a', 'b', 'c']
 
-    >>> dotproduct([1,2,3], [4,5,6])
-    32
-
     >>> data = [20, 40, 24, 32, 20, 28, 16]
     >>> list(convolve(data, [0.25, 0.25, 0.25, 0.25]))
     [5.0, 15.0, 21.0, 29.0, 29.0, 26.0, 24.0, 16.0, 11.0, 4.0]
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index aeebcaf..0e888c4 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -291,6 +291,22 @@ Number-theoretic and representation functions
    .. versionadded:: 3.7
 
 
+.. function:: sumprod(p, q)
+
+   Return the sum of products of values from two iterables *p* and *q*.
+
+   Raises :exc:`ValueError` if the inputs do not have the same length.
+
+   Roughly equivalent to::
+
+       sum(itertools.starmap(operator.mul, zip(p, q, strict=true)))
+
+   For float and mixed int/float inputs, the intermediate products
+   and sums are computed with extended precision.
+
+   .. versionadded:: 3.12
+
+
 .. function:: trunc(x)
 
    Return *x* with the fractional part