Remove PyArray_ReduceWrapper from public API

There are two reasons to want to keep PyArray_ReduceWrapper out of the
public multiarray API:
 - Its signature is likely to change if/when masked arrays are added
 - It is essentially a wrapper for array->scalar transformations
   (*not* just reductions as its name implies -- the whole reason it
   is in multiarray.so in the first place is to support count_nonzero,
   which is not actually a reduction!). It provides some nice
   conveniences (like making it easy to apply such functions to
   multiple axes simultaneously), but, we already have a general
   mechanism for writing array->scalar transformations -- generalized
   ufuncs. We do not want to have two independent, redundant
   implementations of this functionality, one in multiarray and one in
   umath! So in the long run we should add these nice features to the
   generalized ufunc machinery. And in the short run, we shouldn't add
   it to the public API and commit ourselves to supporting it.

However, simply removing it from numpy_api.py is not easy, because
this code was used in both multiarray and umath. This commit:
 - Moves ReduceWrapper and supporting code to umath/, and makes
   appropriate changes (e.g. renaming it to PyUFunc_ReduceWrapper and
   cleaning up the header files).
 - Reverts numpy.count_nonzero to its previous implementation, so that
   it loses the new axis= and keepdims= arguments. This is
   unfortunate, but this change isn't so urgent that it's worth tying
   our APIs in knots forever. (Perhaps in the future it can become a
   generalized ufunc.)

1 files changed, 0 insertions, 13 deletions

diff --git a/numpy/add_newdocs.py b/numpy/add_newdocs.py
index b8223f7c6..f550e2d41 100644
--- a/numpy/add_newdocs.py
+++ b/numpy/add_newdocs.py
@@ -901,14 +901,6 @@ add_newdoc('numpy.core.multiarray', 'count_nonzero',
     ----------
     a : array_like
         The array for which to count non-zeros.
-    axis : None or int or tuple of ints, optional
-        Axis or axes along which a reduction is performed.
-        The default (`axis` = None) is perform a reduction over all
-        the dimensions of the input array.
-    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 original `arr`.
 
     Returns
     -------
@@ -925,11 +917,6 @@ add_newdoc('numpy.core.multiarray', 'count_nonzero',
     4
     >>> np.count_nonzero([[0,1,7,0,0],[3,0,0,2,19]])
     5
-    >>> np.count_nonzero([[0,1,7,0,0],[3,0,0,2,19]], axis=1)
-    array([2, 3])
-    >>> np.count_nonzero([[0,1,7,0,0],[3,0,0,2,19]], axis=1, keepdims=True)
-    array([[2],
-           [3]])
     """)
 
 add_newdoc('numpy.core.multiarray','set_typeDict',