Function PyUFunc_GenericReduction

numpy/core/src/umath/ufunc_object.c:3968–4291

* This code handles reduce, reduceat, and accumulate * (accumulate and reduce are special cases of the more general reduceat * but they are handled separately for speed) */

 * but they are handled separately for speed)
 */
static PyObject *
PyUFunc_GenericReduction(PyUFuncObject *ufunc,
        PyObject *const *args, Py_ssize_t len_args, PyObject *kwnames, int operation)
{
    int i, naxes=0, ndim;
    int axes[NPY_MAXDIMS];

    ufunc_full_args full_args = {NULL, NULL};
    PyObject *axes_obj = NULL;
    PyArrayObject *mp = NULL, *wheremask = NULL, *ret = NULL;
    PyObject *op = NULL;
    PyArrayObject *indices = NULL;
    PyArray_DTypeMeta *signature[3] = {NULL, NULL, NULL};
    PyArrayObject *out = NULL;
    int keepdims = 0;
    PyObject *initial = NULL;
    npy_bool out_is_passed_by_position;


    static char *_reduce_type[] = {"reduce", "accumulate", "reduceat", NULL};

    if (ufunc == NULL) {
        PyErr_SetString(PyExc_ValueError, "function not supported");
        return NULL;
    }
    if (ufunc->core_enabled) {
        PyErr_Format(PyExc_RuntimeError,
                     "Reduction not defined on ufunc with signature");
        return NULL;
    }
    if (ufunc->nin != 2) {
        PyErr_Format(PyExc_ValueError,
                     "%s only supported for binary functions",
                     _reduce_type[operation]);
        return NULL;
    }
    if (ufunc->nout != 1) {
        PyErr_Format(PyExc_ValueError,
                     "%s only supported for functions "
                     "returning a single value",
                     _reduce_type[operation]);
        return NULL;
    }

    /*
     * Perform argument parsing, but start by only extracting. This is
     * just to preserve the behaviour that __array_ufunc__ did not perform
     * any checks on arguments, and we could change this or change it for
     * certain parameters.
     */
    PyObject *otype_obj = NULL, *out_obj = NULL, *indices_obj = NULL;
    PyObject *keepdims_obj = NULL, *wheremask_obj = NULL;
    if (operation == UFUNC_REDUCEAT) {
        NPY_PREPARE_ARGPARSER;

        if (npy_parse_arguments("reduceat", args, len_args, kwnames,
                "array", NULL, &op,
                "indices", NULL, &indices_obj,