Rename math.sum to math.fsum

Doc/library/math.rst

@@ -83,6 +83,16 @@ Number-theoretic and representation functions:
    apart" the internal representation of a float in a portable way.
 
 
+.. function:: fsum(iterable)
+
+   Return an accurate floating point sum of values in the iterable.  Avoids
+   loss of precision by tracking multiple intermediate partial sums.  The
+   algorithm's accuracy depends on IEEE-754 arithmetic guarantees and the
+   typical case where the rounding mode is half-even.
+
+   .. versionadded:: 2.6
+
+
 .. function:: isinf(x)
 
    Checks if the float *x* is positive or negative infinite.
@@ -112,16 +122,6 @@ Number-theoretic and representation functions:
    *x*, and both are floats.
 
 
-.. function:: sum(iterable)
-
-   Return an accurate floating point sum of values in the iterable.  Avoids
-   loss of precision by tracking multiple intermediate partial sums.  The
-   algorithm's accuracy depends on IEEE-754 arithmetic guarantees and the
-   typical case where the rounding mode is half-even.
-
-   .. versionadded:: 2.6
-
-
 .. function:: trunc(x)
 
    Return the :class:`Real` value *x* truncated to an :class:`Integral` (usually

Doc/whatsnew/2.6.rst

@@ -1537,7 +1537,7 @@ Here are all of the changes that Python 2.6 makes to the core Python language.
   * :func:`~math.factorial` computes the factorial of a number.
     (Contributed by Raymond Hettinger; :issue:`2138`.)
 
-  * :func:`~math.sum` adds up the stream of numbers from an iterable,
+  * :func:`~math.fsum` adds up the stream of numbers from an iterable,
     and is careful to avoid loss of precision by calculating partial sums.
     (Contributed by Jean Brouwers, Raymond Hettinger, and Mark Dickinson;
     :issue:`2819`.)

Lib/test/test_math.py

@@ -646,10 +646,10 @@ class MathTests(unittest.TestCase):
         self.assert_(math.isnan(math.sqrt(NAN)))
 
     def testSum(self):
-        # math.sum relies on exact rounding for correct operation.
+        # math.fsum relies on exact rounding for correct operation.
         # There's a known problem with IA32 floating-point that causes
         # inexact rounding in some situations, and will cause the
-        # math.sum tests below to fail; see issue #2937.  On non IEEE
+        # math.fsum tests below to fail; see issue #2937.  On non IEEE
         # 754 platforms, and on IEEE 754 platforms that exhibit the
         # problem described in issue #2937, we simply skip the whole
         # test.
@@ -662,7 +662,7 @@ class MathTests(unittest.TestCase):
         if 1e16+2.0 != 1e16+2.9999:
             return
 
-        # Python version of math.sum, for comparison.  Uses a
+        # Python version of math.fsum, for comparison.  Uses a
         # different algorithm based on frexp, ldexp and integer
         # arithmetic.
         from sys import float_info
@@ -719,13 +719,13 @@ class MathTests(unittest.TestCase):
 
         for i, (vals, expected) in enumerate(test_values):
             try:
-                actual = math.sum(vals)
+                actual = math.fsum(vals)
             except OverflowError:
                 self.fail("test %d failed: got OverflowError, expected %r "
-                          "for math.sum(%.100r)" % (i, expected, vals))
+                          "for math.fsum(%.100r)" % (i, expected, vals))
             except ValueError:
                 self.fail("test %d failed: got ValueError, expected %r "
-                          "for math.sum(%.100r)" % (i, expected, vals))
+                          "for math.fsum(%.100r)" % (i, expected, vals))
             self.assertEqual(actual, expected)
 
         from random import random, gauss, shuffle
@@ -739,7 +739,7 @@ class MathTests(unittest.TestCase):
             shuffle(vals)
 
             s = msum(vals)
-            self.assertEqual(msum(vals), math.sum(vals))
+            self.assertEqual(msum(vals), math.fsum(vals))
 
 
     def testTan(self):

Lib/test/test_random.py

@@ -5,7 +5,7 @@ import random
 import time
 import pickle
 import warnings
-from math import log, exp, sqrt, pi, sum as msum
+from math import log, exp, sqrt, pi, fsum as msum
 from test import test_support
 
 class TestBasicOps(unittest.TestCase):

Modules/mathmodule.c

@@ -352,7 +352,7 @@ FUNC1(tanh, tanh, 0,
 
 /* Extend the partials array p[] by doubling its size. */
 static int                          /* non-zero on error */
-_sum_realloc(double **p_ptr, Py_ssize_t  n,
+_fsum_realloc(double **p_ptr, Py_ssize_t  n,
              double  *ps,    Py_ssize_t *m_ptr)
 {
 	void *v = NULL;
@@ -370,7 +370,7 @@ _sum_realloc(double **p_ptr, Py_ssize_t  n,
 			v = PyMem_Realloc(p, sizeof(double) * m);
 	}
 	if (v == NULL) {        /* size overflow or no memory */
-		PyErr_SetString(PyExc_MemoryError, "math sum partials");
+		PyErr_SetString(PyExc_MemoryError, "math.fsum partials");
 		return 1;
 	}
 	*p_ptr = (double*) v;
@@ -409,7 +409,7 @@ _sum_realloc(double **p_ptr, Py_ssize_t  n,
 */
 
 static PyObject*
-math_sum(PyObject *self, PyObject *seq)
+math_fsum(PyObject *self, PyObject *seq)
 {
 	PyObject *item, *iter, *sum = NULL;
 	Py_ssize_t i, j, n = 0, m = NUM_PARTIALS;
@@ -421,7 +421,7 @@ math_sum(PyObject *self, PyObject *seq)
 	if (iter == NULL)
 		return NULL;
 
-	PyFPE_START_PROTECT("sum", Py_DECREF(iter); return NULL)
+	PyFPE_START_PROTECT("fsum", Py_DECREF(iter); return NULL)
 
 	for(;;) {           /* for x in iterable */
 		assert(0 <= n && n <= m);
@@ -431,13 +431,13 @@ math_sum(PyObject *self, PyObject *seq)
 		item = PyIter_Next(iter);
 		if (item == NULL) {
 			if (PyErr_Occurred())
-				goto _sum_error;
+				goto _fsum_error;
 			break;
 		}
 		x = PyFloat_AsDouble(item);
 		Py_DECREF(item);
 		if (PyErr_Occurred())
-			goto _sum_error;
+			goto _fsum_error;
 
 		xsave = x;
 		for (i = j = 0; j < n; j++) {       /* for y in partials */
@@ -462,8 +462,8 @@ math_sum(PyObject *self, PyObject *seq)
 				   summands */
 				if (Py_IS_FINITE(xsave)) {
 					PyErr_SetString(PyExc_OverflowError,
-					      "intermediate overflow in sum");
+					      "intermediate overflow in fsum");
-					goto _sum_error;
+					goto _fsum_error;
 				}
 				if (Py_IS_INFINITY(xsave))
 					inf_sum += xsave;
@@ -471,8 +471,8 @@ math_sum(PyObject *self, PyObject *seq)
 				/* reset partials */
 				n = 0;
 			}
-			else if (n >= m && _sum_realloc(&p, n, ps, &m))
+			else if (n >= m && _fsum_realloc(&p, n, ps, &m))
-				goto _sum_error;
+				goto _fsum_error;
 			else
 				p[n++] = x;
 		}
@@ -481,10 +481,10 @@ math_sum(PyObject *self, PyObject *seq)
 	if (special_sum != 0.0) {
 		if (Py_IS_NAN(inf_sum))
 			PyErr_SetString(PyExc_ValueError,
-					"-inf + inf in sum");
+					"-inf + inf in fsum");
 		else
 			sum = PyFloat_FromDouble(special_sum);
-		goto _sum_error;
+		goto _fsum_error;
 	}
 
 	hi = 0.0;
@@ -518,7 +518,7 @@ math_sum(PyObject *self, PyObject *seq)
 	}
 	sum = PyFloat_FromDouble(hi);
 
-_sum_error:
+_fsum_error:
 	PyFPE_END_PROTECT(hi)
 	Py_DECREF(iter);
 	if (p != ps)
@@ -528,7 +528,7 @@ _sum_error:
 
 #undef NUM_PARTIALS
 
-PyDoc_STRVAR(math_sum_doc,
+PyDoc_STRVAR(math_fsum_doc,
 "sum(iterable)\n\n\
 Return an accurate floating point sum of values in the iterable.\n\
 Assumes IEEE-754 floating point arithmetic.");
@@ -1021,6 +1021,7 @@ static PyMethodDef math_methods[] = {
 	{"floor",	math_floor,	METH_O,		math_floor_doc},
 	{"fmod",	math_fmod,	METH_VARARGS,	math_fmod_doc},
 	{"frexp",	math_frexp,	METH_O,		math_frexp_doc},
+	{"fsum",	math_fsum,	METH_O,		math_fsum_doc},
 	{"hypot",	math_hypot,	METH_VARARGS,	math_hypot_doc},
 	{"isinf",	math_isinf,	METH_O,		math_isinf_doc},
 	{"isnan",	math_isnan,	METH_O,		math_isnan_doc},
@@ -1034,7 +1035,6 @@ static PyMethodDef math_methods[] = {
 	{"sin",		math_sin,	METH_O,		math_sin_doc},
 	{"sinh",	math_sinh,	METH_O,		math_sinh_doc},
 	{"sqrt",	math_sqrt,	METH_O,		math_sqrt_doc},
-	{"sum",		math_sum,	METH_O,		math_sum_doc},
 	{"tan",		math_tan,	METH_O,		math_tan_doc},
 	{"tanh",	math_tanh,	METH_O,		math_tanh_doc},
 	{"trunc",	math_trunc,	METH_O,		math_trunc_doc},