[GitHub] [incubator-mxnet] hzfan commented on a change in pull request #17866: [Numpy] Add ffi for np.sum, np.var and np.std

[GitBox <gi...@apache.org>]

hzfan commented on a change in pull request #17866: [Numpy] Add ffi for np.sum, np.var and np.std
URL: https://github.com/apache/incubator-mxnet/pull/17866#discussion_r394194735
 
 

 ##########
 File path: python/mxnet/ndarray/numpy/_op.py
 ##########
 @@ -7745,3 +7745,100 @@ def cumsum(a, axis=None, dtype=None, out=None):
            [ 4,  9, 15]])
     """
     return _api_internal.cumsum(a, axis, dtype, out)
+
+
+# pylint:disable=redefined-outer-name, too-many-arguments
+@set_module('mxnet.ndarray.numpy')
+def sum(a, axis=None, dtype=None, out=None, keepdims=None, initial=None, where=None):
+    r"""
+    Sum of array elements over a given axis.
+
+    Parameters
+    ----------
+    a : ndarray
+        Input data.
+    axis : None or int, optional
+        Axis or axes along which a sum is performed.  The default,
+        axis=None, will sum all of the elements of the input array.  If
+        axis is negative it counts from the last to the first axis.
+    dtype : dtype, optional
+        The type of the returned array and of the accumulator in which the
+        elements are summed. The default type is float32.
+    keepdims : bool, optional
+        If this is set to True, the axes which are reduced are left
+        in the result as dimensions with size one. With this option,
+        the result will broadcast correctly against the input array.
+
+        If the default value is passed, then `keepdims` will not be
+        passed through to the `sum` method of sub-classes of
+        `ndarray`, however any non-default value will be.  If the
+        sub-classes `sum` method does not implement `keepdims` any
+        exceptions will be raised.
+    initial: Currently only supports None as input, optional
+        Starting value for the sum.
+        Currently not implemented. Please use ``None`` as input or skip this argument.
+    out : ndarray or None, optional
+        Alternative output array in which to place the result. It must have
+        the same shape and dtype as the expected output.
+
+    Returns
+    -------
+    sum_along_axis : ndarray
+        An ndarray with the same shape as `a`, with the specified
+        axis removed. If an output array is specified, a reference to
+        `out` is returned.
+
+    Notes
+    -----
+    - Input type does not support Python native iterables.
+    - "out" param: cannot perform auto type change. out ndarray's dtype must be the same as the expected output.
+    - "initial" param is not supported yet. Please use None as input.
+    - Arithmetic is modular when using integer types, and no error is raised on overflow.
+    - The sum of an empty array is the neutral element 0:
+
+    >>> a = np.empty(1)
+    >>> np.sum(a)
+    array(0.)
+
+    This function differs from the original `numpy.sum
+    <https://docs.scipy.org/doc/numpy/reference/generated/numpy.sum.html>`_ in
+    the following aspects:
+
+    - Input type does not support Python native iterables(list, tuple, ...).
+    - "out" param: cannot perform auto type cast. out ndarray's dtype must be the same as the expected output.
+    - "initial" param is not supported yet. Please use ``None`` as input or skip it.
+
+    Examples
+    --------
+    >>> a = np.array([0.5, 1.5])
+    >>> np.sum(a)
+    array(2.)
+    >>> a = np.array([0.5, 0.7, 0.2, 1.5])
+    >>> np.sum(a, dtype=np.int32)
+    array(2, dtype=int32)
+    >>> a = np.array([[0, 1], [0, 5]])
+    >>> np.sum(a)
+    array(6.)
+    >>> np.sum(a, axis=0)
+    array([0., 6.])
+    >>> np.sum(a, axis=1)
+    array([1., 5.])
+
+    With output ndarray:
+
+    >>> a = np.array([[0, 1], [0, 5]])
+    >>> b = np.ones((2,), dtype=np.float32)
+    >>> np.sum(a, axis = 0, out=b)
 
 Review comment:
   Remove the space around `=`

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