Function set_matmul_flags

numpy/core/src/umath/ufunc_object.c:347–371

Called at module initialization to set the matmul ufunc output flags */

/* Called at module initialization to set the matmul ufunc output flags */
NPY_NO_EXPORT int
set_matmul_flags(PyObject *d)
{
    PyObject *matmul = _PyDict_GetItemStringWithError(d, "matmul");
    if (matmul == NULL) {
        return -1;
    }
    /*
     * The default output flag NPY_ITER_OVERLAP_ASSUME_ELEMENTWISE allows
     * perfectly overlapping input and output (in-place operations). While
     * correct for the common mathematical operations, this assumption is
     * incorrect in the general case and specifically in the case of matmul.
     *
     * NPY_ITER_UPDATEIFCOPY is added by default in
     * PyUFunc_GeneralizedFunction, which is the variant called for gufuncs
     * with a signature
     *
     * Enabling NPY_ITER_WRITEONLY can prevent a copy in some cases.
     */
    ((PyUFuncObject *)matmul)->op_flags[2] = (NPY_ITER_WRITEONLY |
                                         NPY_ITER_UPDATEIFCOPY |
                                         NPY_UFUNC_DEFAULT_OUTPUT_FLAGS) &
                                         ~NPY_ITER_OVERLAP_ASSUME_ELEMENTWISE;
    return 0;
}


/*