allow keepdims with negative index.

theano/tensor/basic.py

@@ -2655,6 +2655,8 @@ class MaxAndArgmax(Op):
             if len(axis) != 1:
                 list(axis)
                 axis.sort()
+                if axis == range(-x.type.ndim, 0, 1):
+                    axis = range(x.type.ndim)
                 assert axis == range(x.type.ndim), (
                     "MaxAndArgmax does not support multiple"
                     " axes. the max fct supports it.")
@@ -2806,10 +2808,17 @@ def makeKeepDims(x, y, axis):
         axis = range(x.type.ndim)
     elif isinstance(axis, int):
         axis = [axis]
+    newaxis = []
+    for a in axis:
+        if not isinstance(a, int):
+            raise ValueError("keepdims option can be used only with constant axis")
+        if a < 0:
+            a += x.type.ndim
+        newaxis.append(a)
     i = 0
     new_dims = []
     for j, _ in enumerate(x.type.broadcastable):
-        if j in axis:
+        if j in newaxis:
             new_dims.append('x')
         else:
             new_dims.append(i)

theano/tensor/tests/test_keepdims.py

@@ -13,9 +13,14 @@ class TestKeepDims:
         elif isinstance(axis, int):
             axis = [axis]
         i = 0
+        newaxis = []
+        for a in axis:
+            if a < 0:
+                a += x.type.ndim
+            newaxis.append(a)
         new_dims = []
         for j, _ in enumerate(x.shape):
-            if j in axis:
+            if j in newaxis:
                 new_dims.append('x')
             else:
                 new_dims.append(i)
@@ -30,7 +35,8 @@ class TestKeepDims:
 
         # 'max_and_argmax' has two outputs and can be specified with either
         # a single or every axis:
-        for axis in [0, 1, 2, [0], [1], [2], None, [0, 1, 2]]:
+        for axis in [0, 1, 2, [0], [1], [2], None, [0, 1, 2],
+                     [-1], [-2], [-3]]:
 
             op = tensor.max_and_argmax
             keep_param = function([x], op(x, axis=axis, keepdims=True)[0])
@@ -50,8 +56,8 @@ class TestKeepDims:
         # the following ops can be specified with either a single axis or every
         # axis:
         for op in ([tensor.argmax, tensor.argmin]):
-
-            for axis in [0, 1, 2, [0], [1], [2], None, [0, 1, 2]]:
+            for axis in [0, 1, 2, [0], [1], [2], None, [0, 1, 2],
+                         [-1], [-2], [-3], [-1, -2, -3]]:
 
                 keep_param = function([x], op(x, axis=axis, keepdims=True))
                 keep_synth = function([x], self.makeKeepDims_local(x,
@@ -72,7 +78,8 @@ class TestKeepDims:
         for op in ([tensor.sum, tensor.prod, tensor.mean, tensor.var,
                     tensor.std, tensor.all, tensor.any,
                     tensor.max, tensor.min]):
-            for axis in [0, 1, 2, [0], [1], [2], [0, 1], [1, 2], [0, 1, 2]]:
+            for axis in [0, 1, 2, [0], [1], [2], [0, 1], [1, 2], [0, 1, 2],
+                         [-1], [-2], [-3], [-1, -2], [-1, -2, -3]]:
 
                 keep_param = function([x], op(x, axis=axis, keepdims=True))
                 keep_synth = function([x], self.makeKeepDims_local(x,